Red Bull also has taurine in it. I think caffeine + sugar equals extra energy. I feel like I have more energy if I drink one can of mt dew plus a caffeine pill, than if I just took a caffeine pill alone. As an experiment, I tried to drink a bunch of caffeine free soda, to see if the tons of corn syrup (sugar) would give me energy, I got bloated and had to pee a lot, but no energy boost. I think the b vitamins and taurine help somewhat in the Red Bull, but I would bet without the caffeine and sugar it wouldn't work. I never tried sugar free Red Bull, does it work as well, do they put extra caffeine in it, since you can't get the sugar boost. I know that mt. dew isn't healthy, and I don't have any science behind my experiment, I'm just posting how it worked for me.