Nothing wrong with coffee or green tea or diet free drinks. People have dropped huge weight on crystal lite drinks instead of water.Check old posts on this forum.
Drink low calorie /zero calorie sweetners in your coffee or tea and would use maybe milk substitue or drink it black.Also tiny bit of 1% or skim milk wouldn't think would be a big deal.
I took green tea in capsule form on my fast. Helped with energy and possibly sped up weight loss and also think helped in beginning with hunger.