Thanks everyone for your suggestions
Trev seems more or less ok now, he's even had some food, but doesn't want anything alcoholic, at least not today. He said he stuck to beer, which he normally drinks when we go out, but just had too much. He doesn't drink that much anyway, and was out with more regular drinkers last night. He'll probably be fine tomorrow, and I doubt he'll do it again.
I'm not mad with him, but I'm not very sympathetic either.