I think everything affects everyone differently, though there might be some things that commonly help or hurt fluency. I can be very fluent while drunk, yet I know someone who's stuttering gets worse when they drink. I haven't looked into as much as I'd like to, but I believe marijuana helps. It has something to do with the receptors that are fulfilled by marijuana and the ones that are responsible for stuttering. Please don't take this as someone trying to be an expert, I have very little knowledge of it and encourage you to look into it for yourself.