I've ingested mostly just psychedelics. A little MDMA. And more than my share of cannabis. I really don't think any of them had a marked affect on my speech, positive or negative. As far as stimulants, I don't even drink coffee anymore because I'd get the jitters. And even then, no effect. I have found that a decent dose of nootropics like those in the "AlphaBrain" supplement (the old formula, the new one sucks) can cause me to be slightly more fluent but more than that it caused me to be much more talkative and break through shyness a bit better. All that said, the only thing I've found to truly help with fluency is daily meditation and Eastern religion. Why you ask? Easy, when you have an awakening experience or can grasp it conceptually you can easily remove your attachment to what people are thinking of you. In a literal sense, they are you. And in that way nervousness seems silly. So I've found my fluency was based on how confident I am feeling (also related to energy levels and sleep). As well as having enough breath and inserting intentional pauses for thought (where the meditation breathing practice comes in. A side benefit is that I come off more intelligent than I am. Booyah. And of course the obligatory drug warning to anyone reading this: Don't be an idiot. EDIT: I wanted to add about using drugs. Typically using them for emotional problem solving leads to addiction. As people who stutter, we carry a ton of trauma from being childhood outcasts. So again, proceed with extreme caution.