Don’t worry. Apart from black coffee, there are many choices for you to have during the fasting hours, just make sure you have no calorie intake.
Here are some examples of calorie-free drinks:
Plain tea (e.g. black, green, herbal)
Sparkling water (OR flavored with zero-calorie)
Citrus OR berry flavored water (a few fruits slices)
Diet/no-sugar soda (Diet coke, no sugar Coke)
You may add 1 tablespoon of milk or unsweetened plant-based milk, and a small amount of artificial sweetener in your drinks to enhance the flavor if you can’t have them plain.