Good news: fasting doesn't mean going thirsty. Water is a great friend during a fast, and you should drink plenty of it. Fizzy water counts too, if you like the bubbles.
Plain black coffee and unsweetened tea, whether black, green or herbal, are usually fine for most people. They have hardly any calories, and many find a warm mug takes the edge off a hunger wave nicely.
What usually ends a fast is anything with a meaningful number of calories. That means sugar, honey, syrups, juice, fizzy drinks, smoothies and milky bubble tea. A big milky latte counts as a meal, even though it's in a cup. A tiny splash of milk is a grey area, so if you'd like one clear rule, make it: nothing with calories until your eating window opens.
Sweet-tasting zero-calorie drinks are another grey area. Some people get on fine with them, while others find the sweetness makes cravings louder. You know yourself best, so try it and see.
A couple of friendly tips. Sip water regularly through the day, and drink a bit more if your wee is dark yellow. Coffee on an empty stomach can make some people jittery or queasy, so go easy. And if a drink makes you feel odd, pop a quick note in Step Step so you remember for next time.
What can you drink while fasting?
The safe list is short and friendly. Still water and fizzy water are always fine. Plain black coffee and unsweetened tea, whether black, green or herbal, are usually fine too, since they contain almost no calories.
That list is the same whether you are doing a 12:12 overnight fast or something longer. If you want one simple rule, make it: nothing with calories until your eating window opens.
Temperature matters less than you might expect. A hot mug is comforting on a cold morning, and ice water is refreshing in summer. Choose whatever makes it easiest to keep sipping.
Alcohol is best left for your eating window. It contains calories, it can drop blood sugar on an empty stomach, and it often leads to snacking.
Does coffee break a fast?
Black coffee has only a couple of calories per cup, so most people treat it as part of the fast. Add milk, cream, sugar, syrup or a flavoured creamer and you are drinking calories, which in most definitions ends the fast.
A small splash of milk is a grey area. If you are fasting for a gentle reason, such as tidier eating, a dash is unlikely to matter much. If you want a clean line, wait until your window opens.
Coffee on an empty stomach can cause jitters, nausea or heartburn for some people. If that is you, try a smaller cup, drink it with water, or switch to tea. Caffeine late in the day can also spoil sleep, which tends to make the next day's hunger louder.
If you drink several cups a day, notice how you feel by mid-morning. A big black coffee on no food can feel sharp at first and then flat. Pairing it with a glass of water, or switching one cup for tea, often smooths that out.
What about tea, diet drinks and sweeteners?
Plain tea of any kind is fine. Herbal teas such as peppermint, ginger or chamomile are pleasant and warm. Watch out for blends with added sugar, honey or dried fruit pieces that sweeten the cup.
Zero-calorie fizzy drinks and sweeteners are debated. They do not add meaningful calories, but some people find the sweet taste keeps cravings going. Others get on fine with them. Try a week with and a week without, and see what you notice.
Things that clearly end a fast include juice, smoothies, sweetened coffee, milk tea, fizzy drinks with sugar, sports drinks and alcohol. Bone broth, oat milk and milky bubble tea all contain calories too.
How much should you drink while fasting?
Plenty of the water you normally get comes from food, so when you eat less you may need to drink more to stay level. A pale yellow wee is a handy sign you are doing fine, and dark yellow suggests you need more.
Space your drinks across the day rather than gulping a litre at once. In hot weather, or after exercise, drink more. If you have kidney, heart or blood pressure conditions, ask your doctor how much fluid suits you. The Water Intake Calculator on this site can give you a rough daily starting point.
It also pays to read labels. Flavoured waters, protein waters, vitamin drinks and some sparkling waters contain sugar or juice, and cold brew or canned coffee is often sweetened. If a drink has a nutrition label with calories above a few per serving, treat it as part of your eating window. Electrolyte tablets vary too, and many contain a little sugar. If you fast for longer than a day, speak to a doctor about fluids and salts first.
Common questions
Does black coffee break a fast?
Plain black coffee has almost no calories, so most people count it as fine during a fast. Milk, sugar and syrups add calories and usually end the fast.
Can I drink tea while fasting?
Yes, unsweetened tea, including green, black and herbal, is generally fine. Avoid honey, sugar and milky teas until your eating window.
Do zero-calorie drinks break a fast?
They add almost no calories, so technically no. Some people find the sweetness increases cravings, so it is worth testing how you feel.
How much water should I drink when fasting?
There is no single number. Sip regularly through the day and aim for pale yellow wee. Drink more in hot weather or after exercise.
Updated October 25, 2026
This is general information, not medical advice. Check with your doctor before you start fasting, especially if you have a health condition, are pregnant or take medication.
