You can drink water (actually, it's a must!). Tea and coffee are also totally OK while fasting. It is highly recommended to drink them plain. However, a super tiny splash of milk or creamer added to your coffee won’t do much harm. The same goes for a slice of lemon in your water.
Despite that, we still advise you to stay strong and wait until your eating window starts to use milk, creamer and drink other beverages that aren't calorie-free.
Then, you are free to drink whatever you want!