No caffeine in them, they'd have to show it if there was. The B vitamins are where the energy is coming from.I don't see any reason you can't have them, but I personally thing energy drinks are a waste and your better off both from a results stand point and money to just drink more coffee.
Actually they dont have to list caffeine, if its incidental, just anhydrous due to is unstable nature. I used to work with the FDA, AMA on stuff like this for pharmaceuticals.