I drink a lot of Coke Zero but the caffeine in it doesn't bother me. But a bit like WildFlowerChild, sometimes coffee makes me weak, shaky, starving and upsets my stomach. It's too bad because i love how it tastes. But the last time i had it i had a stomach ache that lasted several hours so i know i'm tempting fate if i drink it. Sometimes i just say f*&k it and do it, if things are slow in my drop-in. I've never tried those energy drinks. After my time i guess. I'm 50.