This is short term though. Providing a player can take a line just when needed yeah could work. But i highly doubt anyone can take a line only when needed. Coke is highly addictive.
Unlike international competitions where you are required to perform at max level a handful of weeks a year winning a cup requires a long grind. Yeah that line might help you in double OT of game 7 in the scf but for it to be helpful you need to win enough beforehand for a very long period of time.
I see what you're saying, and absolutely it is detrimental for you in the long term, but I think it's much more long term than that.
If there are stock brokers, and teachers, and lawyers and doctors who can manage their coke habit, I have no doubt an NHL player could.
At the risk of sounding like I'm diminishing the addiction potential of it (which I'm not), Plenty of people use cocaine regularly but not daily. Lots of users fall into the once a week category, as it's used in conjunction with going out on the town on the weekends.
I agree the scenario of using it before double OT is unlikely (though I bet this has happened in the past). I just think it absolutely has the potential to give someone a competitive edge that others don't.