Gerhard Wilder, 46, from Bochum in western Germany, was wedged so tightly in the drain that he had to be freed by firefighters.
He has now pledged to stay off beer and go on a diet after embarrassing pictures of the incident were shown all over German media.
A motorist raised the alarm after he went to move a car parked next to the drain and spotted the trapped man.
He said: "I heard a voice saying help and at first I didn't see him.
"Then I tried to pull him out but he was wedged tight. He didn't see that jokers had removed the drain cover as he staggered home."
Firemen spent an hour removing part of the drain before they could pull the man free.
A fire brigade spokesman added: "He did not know how the drain cover had got removed - and denied doing it himself.
"After he was freed he walked home on his own - I think he was very embarrassed by it all and promised he would never drink again. He also said he planned to lose weight."