Charlie Sheen -- a recovering everything-aholic -- hit the Guns N' Roses concert HARD this weekend ... REALLY HARD ... at least judging by the way he slurred through a Q&A with photogs after the show.
Sheen was leaving the Palladium in Los Angeles Friday night ... when he fired off a sloshy torpedo of truth about the band ... hinting they'd be BETTER with Slash.
We also asked about Sheen's favorite GNR song ... and we're pretty sure he cracked a heroin joke ... telling us, "Mr. Brownstone ... imagine that?!"
FYI -- Mr. Brownstone is a slang term for the drug.
As Sheen pulls away, one pap says, "I party like Charlie Sheen" ... to which the actor replies, "And you're still alive?!"
Yeah, we're amazed too.