I’ve “bathed” after a fashion in the men’s room between legs of international flights. As for clothes, I don’t know.
Workers like janitors and baggage handlers have places where they can clean up. Uniforms might be available there, some of look like normal cloths only in limited colors. And then there is lost luggage. If he had a United managers pass he may have had access to staff common areas without having to swipe or he could just follow someone in. And of course no one pays attention to someone sleeping in a huge airport.
O’Hare Airport is probably a more comfortable place to spend a Chicago winter than on the street. I wonder how many homeless people try to stay there, or in other large airports.
I can attest that I have seen homeless people sleeping in the baggage claim area at the Minneapolis-St. Paul airport, so I would assume they do at O’Hare, too. But baggage claim is of course outside the secure area and can be accessed by anyone, while this man stayed in the concourse.
I had an hour to kill at MSP last summer and went up to the observation deck. I was the only person there to observe, but there were half a dozen sleeping (or trying to). Probably a lot less traffic than at baggage claim, should the need arise.
So, no news here, except the charge of petty theft and misuse of an ID badge that he might have found. My personal record is 21 hours, at Guam and at Port of Spain.