I get to choose the drink, not the person. But then again you get to choose the person, not the drink. So I think it balances itself out. If I got to choose the person then choosing the drink would be irrelevant. The only one that can confirm nothing happened to Martin is Martin and obviously we can't chat with him right now. I would assume that the drink takes effect either that night, or the following day. There are multiple possibilities.
I wonder if certian people are matched to certain drinks.