Cocaine can increase focus, and allow you to work through pain, so I think it could be useful in sports. It's basically a super upper, no? (Cocaine is definitely the drug I'm tempermentally susceptible to being addicted to.)
Go with Red Bull. Cheaper, and less likely to end your tennis career.
Haven't Tour de France cyclists been busted for meth use? (Many years ago.)
I have a feeling a co-worker uses coke as a maintenance drug, but I have no proof. Well, other than the manic mood swings.
I've seen enough people on coke to think that I can reliably tell whether or not someone is doing it. I wish I could take all y'all up to the bar, point out a couple of people and say "Here, this is what it looks like."
Once a bunch of people (myself included) suspected a friend of doing cocaine, as he was constantly going out, despite working two jobs (and he was always out of money) and he had the mood swings thing too. Turned out he wasn't on coke. Oops. (eta: some folks did the intervention thing)
and... post 10000 crept up on me - hadn't noticed we were that close....