There was an old military saying that Fred Colon used to describe total bewilderment and confusion. An individual in that state, according to Fred, "couldn't tell if it was arsehole or breakfast time".
This had always puzzled Vimes. He wondered what research had been done. Even now, with his mouth tasting of warmed-over yesterday and everything curiously sharp in his vision, he thought he'd be able to tell the difference. Only one was likely to include a cup of coffee, for a start.