What Can You Drink While Fasting? The Complete List

One of the most common questions about intermittent fasting has nothing to do with food. It is about what you can drink. Can you have coffee? What about tea with honey? Does sparkling water count? Will that splash of cream ruin everything?

The answers depend on your fasting goals. Someone fasting for autophagy has different rules than someone fasting purely for weight loss. This guide breaks down every common beverage with a clear verdict so you never have to guess.

Quick Answer: Water, black coffee, and plain tea are safe during any fast. Zero-calorie drinks like sparkling water and black coffee will not break your fast. Anything with calories, sugar, or protein -- including milk, juice, and most smoothies -- will break your fast. Some drinks like diet soda and lemon water fall into a gray area depending on your goals.

The Fasting Drinks Table

Beverage	Breaks Fast?	Notes
Water	NO	Always safe. Drink plenty.
Black coffee	NO	May enhance fat burning and autophagy. Full guide.
Plain green tea	NO	Contains catechins that may support fasting benefits.
Plain black tea	NO	Zero calories. Safe for all fasting goals.
Herbal tea (unsweetened)	NO	Most varieties are fine. Avoid fruity blends with added sugars.
Sparkling water / seltzer	NO	Plain or naturally flavored without sweeteners.
Water with electrolytes	NO	Sodium, potassium, magnesium without sugar or calories.
Lemon water (small squeeze)	MAYBE	Minimal calories. Likely fine for weight loss fasting. Details.
Apple cider vinegar (diluted)	MAYBE	1-2 tbsp in water is negligible calories. May support fasting.
Diet soda	MAYBE	Zero calories but artificial sweeteners may trigger insulin in some people.
Coffee with cream/milk	YES	Even a splash adds calories and triggers digestion.
Coffee with sugar	YES	Sugar breaks a fast immediately.
Bulletproof coffee	YES	High in calories from butter/oil. Breaks a fast.
Juice (any kind)	YES	High in sugar and calories. Breaks a fast.
Milk	YES	Contains lactose (sugar), protein, and calories.
Smoothies	YES	Calories and macronutrients. Definitely breaks a fast.
Bone broth	YES	Contains protein and calories, though minimal.
Protein shakes	YES	Designed to deliver calories and protein.
Alcohol	YES	Contains calories and impairs metabolic processes.
Coconut water	YES	Contains natural sugars and calories.
Kombucha	YES	Most brands contain sugar and calories.
Sports drinks (Gatorade, etc.)	YES	Full of sugar and calories.

Understanding the "Maybe" Category

The drinks in the gray area deserve more explanation because context matters.

Diet Soda and Artificial Sweeteners

Diet sodas contain zero calories, which technically means they should not break a fast. However, research is mixed on whether artificial sweeteners trigger an insulin response. A 2020 study in Cell Metabolism found that some artificial sweeteners can alter gut microbiota and glucose tolerance, though the effect varies by individual and sweetener type.

If your primary goal is weight loss through calorie restriction, diet soda during your fast is unlikely to derail your progress. If you are fasting for autophagy or metabolic health, it is safer to avoid it.

Lemon Water

A squeeze of lemon in water adds roughly 1 to 3 calories. This is metabolically negligible and will not trigger a meaningful insulin response. Most fasting experts agree that lemon water does not break a fast in any practical sense. It can also make plain water more palatable, which helps with hydration.

Apple Cider Vinegar

One to two tablespoons of apple cider vinegar diluted in water contains about 1 to 3 calories. Some research suggests ACV may actually enhance fasting benefits by improving insulin sensitivity. Read the full breakdown of ACV and fasting.

Water: The Foundation

Water is the most important thing you consume during a fast. Dehydration is the primary cause of common fasting side effects like headaches, fatigue, and dizziness. During fasting, your body excretes more water and electrolytes than usual, particularly in the first few days of a new fasting practice.

Aim for at least 8 glasses of water per day during your fasting window. Many people find they need more. Adding a pinch of sea salt or sugar-free electrolytes can help with absorption and prevent the mineral depletion that causes fasting headaches.

Sparkling water and mineral water are equally valid. The carbonation does not affect your fast, though some people find it can cause mild bloating on an empty stomach.

Coffee and Tea: The Fasting Allies

Black coffee and plain tea are not just permitted during fasting -- they may actively enhance it.

Coffee contains caffeine, which increases metabolic rate and promotes fat oxidation. A study published in the American Journal of Clinical Nutrition found that caffeine can increase metabolic rate by 3 to 11 percent. Coffee also contains chlorogenic acid, which may support autophagy. For the complete guide, see coffee and intermittent fasting.

Green tea provides L-theanine alongside caffeine, creating a calm focus without the jitteriness some people experience with coffee. The catechins in green tea, particularly EGCG, have been shown to support fat oxidation and may enhance autophagy.

Black tea and herbal teas are also safe choices. Just avoid any variety with added sugars, honey, or dried fruit pieces that contain calories.

The critical rule: no additions. No sugar, no honey, no milk, no cream. These all add calories and trigger metabolic responses that end your fasted state. If you cannot drink coffee black, consider cold brewing, which produces a smoother, less bitter flavor.

What About Bone Broth?

Bone broth technically breaks a fast because it contains protein and calories, typically 30 to 50 calories per cup. However, many fasting protocols, particularly those focused on gut health and longer fasts, permit bone broth during the fasting window.

The rationale is practical: bone broth provides essential electrolytes, supports gut lining repair, and makes extended fasts more sustainable. If you are doing a 36-hour fast or longer, a cup of bone broth may help you complete the fast successfully, which matters more than strict caloric purity.

For standard 16:8 or 18:6 fasting, save the bone broth for your eating window. For extended fasts, it is a judgment call. Read the full bone broth and fasting guide.

Common Mistakes with Fasting Drinks

Adding "just a little" cream to coffee. Even a tablespoon of cream contains about 50 calories and enough fat to trigger digestion. It breaks your fast.

Drinking flavored water with hidden sweeteners. Check labels carefully. Many flavored waters contain sucralose, stevia, or other sweeteners. While these are unlikely to break a fast for weight loss purposes, they can for stricter fasting goals.

Neglecting electrolytes. Many people drink plenty of water but skip electrolytes, leading to headaches, muscle cramps, and fatigue. Sodium, potassium, and magnesium are essential, especially during longer fasts.

Overloading on caffeine. Coffee on an empty stomach can increase cortisol and cause anxiety or GI discomfort. Limit yourself to 2 to 3 cups during your fasting window and consider switching to tea later in the day.

Drinking alcohol during eating windows excessively. While alcohol is obviously off-limits during fasting, excessive drinking during eating windows can impair sleep, increase next-day hunger, and undermine the metabolic benefits of fasting.

How Your Fasting Goal Changes the Rules

Weight loss: You can be slightly more lenient. Anything under 5 to 10 calories is unlikely to affect your results. Diet soda, lemon water, and ACV are all fine.

Autophagy: Be stricter. Even small amounts of protein or amino acids can inhibit autophagy pathways. Stick to water, black coffee, and plain tea.

Insulin sensitivity: Avoid anything sweet-tasting, even if calorie-free. Some research suggests that sweet taste alone may trigger a cephalic phase insulin response, though this remains debated.

Gut rest: Stick to water only. The goal is to give your digestive system a complete break, which means avoiding anything that stimulates digestive enzyme production.

Understanding what breaks a fast depends entirely on what you are trying to achieve.

How Fasted Helps

Fasted includes a built-in guide to fasting-safe beverages so you can check what is allowed without leaving the app. The fasting timer shows your current fasted state, helping you stay motivated to stick with approved drinks. Use the meal logging feature during your eating window to track your hydration and nutrition.

Frequently Asked Questions

Does flavored sparkling water break a fast?

If it contains zero calories and no artificial sweeteners, it does not break a fast. Check the label for hidden sugars or sweeteners. Brands like LaCroix and Perrier are generally safe.

Can I drink coffee with stevia while fasting?

Stevia is calorie-free and has minimal impact on blood sugar in most people. For weight loss fasting, it is likely fine. For autophagy-focused fasting, it is better to go without any sweetener.

How much water should I drink while fasting?

Aim for at least 2 to 3 liters per day, more if you exercise or live in a warm climate. Signs you need more water include dark urine, headaches, and dizziness. Adding a pinch of salt helps with absorption.

Can I drink energy drinks while fasting?

Sugar-free energy drinks technically have zero calories, but they often contain artificial sweeteners, amino acids, or other additives that may affect your fast. They also tend to be harsh on an empty stomach. Black coffee or green tea are better alternatives.

Will a splash of almond milk break my fast?

Unsweetened almond milk contains about 3 calories per tablespoon. While this is minimal, it does technically break a strict fast. For weight loss purposes, a small splash is unlikely to matter. For autophagy, skip it.