Cole recommends staying away from caffeine as it can at like a diuretic but I think that’s more coffee than green tea. My advice follow the snake diet as closely as possible weigh your self daily and see how what you do changes. I used to drink 1 cup of coffee daily and 2 cups of green tea. I’ve only been on snake diet for 11 days and have lost 10lbs already. Around the 3 or 4 day I had a headache from withdrawals and then I was fine. No more coffee in the morning. Ketones seem to be enough for me. So in short do what you want as long as you make progress, but follow the diet as closely as you can and you might surprise your self.