Although you don't eat anything while fasting, make sure that you drink only noncaloric drinks during your intermittent fast, the most important being water. In fact, you should drink a minimum of eight glasses of water, which can help you feel fuller and can ensure you're staying hydrated throughout the day.
Other noncaloric drinks you can consume during your intermittent fast include the following:
Black coffee
Black tea
Green tea
Herbal teas, such as peppermint, chamomile, or rooibos
Sparkling water
Keep caffeine to a minimum, if you can because too much isn't good for you or your fast. Try not to exceed two cups of coffee in one day (or approximately 200 milligrams of caffeine).
You can easily sneak calories into beverages with milk or sugar, so be careful. Drinking unsweetened tea or not adding half-and-half to your morning cup of coffee can seem difficult at first, but the benefits of intermittent fasting far outweigh the initial discomfort of giving up your routine.
If you start to add a dash of cream here or a packet of sugar there, you may soon find that you aren't fasting at all but instead spiking insulin levels and not allowing your body to reap the full benefits of the fasting period. Remember, you're only taking a break from eating once or twice a week so be strong. You can do it.
When first trying out intermittent fasting, some people experience headaches. If you experience headaches, you aren't dehydrated, but rather you're experiencing a common withdrawal symptom. Be mindful of the amount of caffeine you consume during your fast, because caffeine acts as a diuretic.
If you consume too many caffeinated beverages while fasting, without drinking enough water or herbal tea as well, you may get a caffeine headache or become dehydrated.