What Can You Drink During Intermittent Fasting?

One of the first questions people ask when they start intermittent fasting is simple: what can I actually drink? Get this wrong and you break your fast without even knowing it.

The good news is the rule is simple. The bad news is most people are already breaking it.

The Short Answer

During a fast, you can drink:

• Water (still or sparkling)
• Plain black coffee (no milk, no sugar, no creamer)
• Plain herbal tea (nothing flavoured or sweetened)
• Plain green or black tea

That's it. Anything else risks breaking your fast.

Why These Are the Only Safe Options

Fasting works by keeping your insulin levels low. When insulin drops — typically after 12 or more hours without food — your body switches from burning glucose to burning stored fat. This is the metabolic shift that drives weight loss, increased energy, and cellular repair.

Anything that triggers an insulin response ends that process. Even small amounts.

Water, plain coffee, and plain tea contain essentially zero calories and do not spike insulin. That's why they're safe. Everything else is a gamble — and most of the time, you lose.

What Breaks Your Fast

The following drinks break a fast, even in small amounts:

• Milk or cream in coffee — yes, even a splash. Milk contains lactose (sugar) and protein, both of which trigger insulin.
• Sweetened drinks — soda, juice, flavoured water, sports drinks, lemonade.
• Alcohol — completely halts fat burning and stresses the liver.
• Protein shakes or meal replacement drinks — these are food.
• Bone broth — contains protein and calories. Save it for eating windows.
• Diet soda — controversial, but artificial sweeteners can trigger an insulin response in some people and create cravings. Best avoided.
• Bulletproof coffee (coffee with butter or MCT oil) — contains calories. Breaks a clean fast, even if some protocols allow it.

What About Black Coffee?

Black coffee is one of the most fasting-friendly drinks you can have. It contains virtually no calories, does not raise insulin, and may actually enhance the benefits of fasting by boosting fat oxidation and mental clarity.

Many fasters report that a cup of black coffee around the 14–16 hour mark of a fast dramatically reduces hunger and sharpens focus — exactly the effect described in Intermittent Fasting in Practice.

If you're not used to black coffee, give yourself a week to adapt. The bitterness fades quickly once your palate adjusts.

What About Sparkling Water?

Plain sparkling water (carbonated water with no flavouring, sweeteners, or additives) is completely fine during a fast. It can actually help with hunger by creating a feeling of fullness in the stomach.

If it has any added flavour, citric acid, or sweeteners — check the label carefully. Many "sparkling waters" are secretly sweetened.

Herbal Tea Tips

Herbal teas are excellent during a fast — they come in a huge variety of flavours, have zero calories, and can make long fasting windows much easier to get through.

Watch out for:

• Teas with added sugar or honey
• Fruit-flavoured teas that contain actual fruit pieces (technically food)
• "Wellness" teas with added supplements that have calories

Plain chamomile, peppermint, ginger, and green tea are all safe.

The Practical Rule

If it has calories, it breaks the fast. If it could trigger insulin — even without obvious calories — it probably breaks the fast. When in doubt, stick to water.

This isn't about perfection. One splash of milk won't destroy months of progress. But if you're doing it every morning and wondering why your results have stalled, that's likely why.

Ready to go deeper? Intermittent Fasting in Practice covers not just what to drink, but exactly what to eat during your eating window to make fasting feel effortless — no hunger, no cravings, no white-knuckling. Get it on Amazon and claim 3 months free app access at /redeem.

Frequently Asked Questions

Can I put anything in my coffee while fasting? No. Black coffee only. Even a small amount of milk or cream contains enough protein and sugar to trigger insulin and technically break your fast.

Does sparkling water break a fast? Plain sparkling water does not break a fast. Flavoured or sweetened sparkling water does — always check the label.

Can I drink green tea while fasting? Yes. Plain green tea is perfectly safe during a fast. It may even enhance fat burning through its catechin content.

How much water should I drink while fasting? At least 2–3 litres per day. Fasting can have a mild diuretic effect, especially in the first week. Staying well hydrated also helps reduce hunger.

Can I drink herbal tea during a fast? Yes — as long as it has no added sugar, honey, or flavouring. Plain herbal teas are one of the best tools for getting through long fasting windows comfortably.

This article is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional before starting any fasting protocol, especially if you have an existing health condition.