Sorry for resurrecting such an old thread, but I noticed the same thing. Last year I was keeping track of my weight loss quite thoroughly for some time, weighing myself twice a day, first thing in the morning and before going to bed—while on keto. I noticed I was losing more weight in the days I consumed a can of sugar-free Red Bull. Not much difference, mind you, but enough to be noticeable. I just found this thread, so I thought I could add my 2 cents.