No food is allowed during the fasting period, but you can drink water, coffee, tea and other non-caloric beverages. Some forms of intermittent fasting allow small amounts of low-calorie foods during the fasting period. Taking supplements is generally allowed while fasting, as long as there are no calories in them.

How fast do caffeine pills kick in?

It can take about an hour for caffeine pills to be fully absorbed in the bloodstream and take full effect. Depending on body composition, it can take anywhere between 3 and 12 hours for the body to metabolize half of the caffeine present.

Will supplement pills break a fast?

Supplements may be used during fasting periods, although some may be better absorbed with food. Supplements that contain calories or sugar are more likely to break your fast.