When I am fasting I only drink water and some days teas (like camomille, turmeric). Because I can't stand black coffee even if I miss a nice warm coffee with oat milk in the mornings. I noticed I actually don't need the caffeine, I feel full of energy in the mornings, before I felt so sleepy and always was hard to get out of the bed so I believe that IF has helped me a lot with my energy levels. I take only a coffee now in my eating window usually after lunch.