I find that when I'm actively on them, my fluency is great, similar to drinking. But I've not noticed any long-term effects specific to my fluency. I do feel a lingering sense of calmness / lower anxiety after a trip, which does positively contribute to my fluency, though. I do second what ElianM said about daily L-Theanine and CBD having a significant impact on lowering my stress / anxiety, which in turn helps me be more fluent.