sugar free redbull is a thing, pretty much no calories. it's not bad per se, but being addicted to caffeine isnt all that great like i am right now, but the b vitamins (specifically b12, which gets your blood going) are completely safe, and taurine is just understudied but i'm sure it's fine. dont drink more than 1 a day. coffee is fine as well, instant coffee packs 3 in 1 with sugar are p good for energy.