Theo had found Sam's ultimate weakness: social awkwardness. At the implication that he didn't trust the shady stranger on the well-known criminal port, Sam stood up straight and shook his head, immediately remembering where he was and who he was, that he didn't want to get beaten up in a dark alley by Theo's thug friends he surely had. "No! N-No. Sorry. Um..."
Obediently now he looked between the three cups, pretty sure that he'd be wrong no matter what. After a moment he pointed to the leftmost one, a random guess, wanting to get the game over with more than anything else. "Tha-that one."