Suika's already really smart and alert, though. (and in some cases, focused, if she has a particular task she wants to do)
Heck, her dialogues in all official works tend to be more coherent (and brutally honest) than the vast majority of Touhou characters. Granted, lots of people when they're drunk get really REALLY brutally honest, I've noticed (which is probably done by ZUN on purpose, then)
It's generally stated that oni hold their alchohol really well. So I suppose the end result is that Suika loses all social inhibitions (which is why she just flat out states impolite-but-honest criticisms to everyones' face. Again, I've seen drunk people do this often) but still doesn't become a complete loon, contrary to her battle animations.