You can have small amount of plain tea more so if it is decaf and moderate plain coffee and you can drink Apple cider vinegar.. There are things you can have other than water … caffeine will kick you out.. I just don’t know how much it takes to kick you out. But just sticking to water is best.
How long have you been doing keto for? I don’t think those will kick you out of your fasted state but they are heavy in chemicals. C4 has creatine which is really for mass building. It can put on weight. They will say they use creatine nitrate which is non bloating but I still got extremely bloated on it. Part of this program is to reduce inflammation and many of these energy supplements have a lot of chemicals. Supplements started stalling me. I only drink coffee now.