I only tried drunken cycling once. I thought it would be a fun idea to ride down the road no-hands, with my eyes closed, laughing wildly... Fortunately, I opened my eyes about 1 second before I would have crashed into the back of a parked van, and managed to swerve round it. That kind of sobered me up...
A colleague had been to a party and was riding back along the Rochdale canal towpath in the early hours, the worse for wear. He managed to headbutt a low-flying canal bridge and knocked himself into the canal, which was nearly freezing at the time. He said that he sobered up pretty quickly too! If he actually knocked himself out, then he almost certainly would have drowned because there was anybody about to rescue him.