Originally Posted by BarracksSi

I'm not a coffee drinker, so I can only comment on half of the topic --

As a brasswind musician, namely low brass (trombone, tuba, etc), I found that caffeine from soda pop made me play worse. Everything felt harder, and the extra effort manifested itself in my sound. If I eliminated caffeine, and even if I continued with caffeine-free sodas, I played better, with more consistency and a more even tonal character.

I'm just one data point, although one of my band friends noticed the same thing with his playing. I also haven't experimented with how it affects my cycling. But as a brass player, I always play better, and with more ease, if I don't have any caffeine in my system.