This seems like a detail that should go here too. I was reading a Mumbai thread asking about how to get the Maelstrom to drink tea and it was posted that there was a way to tell within the level itself, since otherwise it is random.
This must have been something I just missed during Hitman 2’s launch and never went back to learn. Anyway, there is a TV in the Slum Square that (after some news) advertises the tea the Maelstrom would drink if you offer it to him. It changes each retry to the color representing the table you serve the tea in the Tea Shops area.
Off the top of my head, the only other random poison spot I can recall is the Honey/Sugar offer to Alma Reynard in Nightcall. Is there some type of tell for that one too?