He's serious. She can tell he's serious because of the expression on his face and the way he's going through the experience. But also? It's a total load of bullshit. The having to drink the piss, anyway. Who the hell knows about the wave of pee at this point? But is it even reasonable to say something about that to the person who clearly has some trauma around it? Not anywhere near as reasonable as downing the rest of her drink.