That's not what he's quoted as saying. It doesn't say he slept "in a bin". You've put your own interpretation on it and changed the meaning quite radically.
There's an extra bit of detail in the local paper:
"In his witness statement, Mr Robb detailed how Mr McKeague had previously passed out through drink and awoken the following morning in the toilets of a McDonald’s restaurant in Bury St Edmunds, and on a separate occasion fell asleep on a bench outside a Tesco store in the town.
He said that on a stag do in Liverpool in August 2016 Mr McKeague climbed up a drainpipe and through a window of the accommodation where he was staying, getting into a room that was not his and falling asleep there."
'There was no worry about him', says doorman who spoke to Corrie McKeague
People have said that Corrie told them that night that he was going to walk home. He had already had a sleep in a shop doorway when he arrived at the horseshoe. I'm convinced that he relieved himself behind the bins and walked away up Short Brackland without being caught by the rotating camera. Sooner or later he may have accepted a lift or met with some kind of mishap, but that could have been anywhere, perhaps well away from town.