I could sleep standing up in a closet if I had to.

Alexei said you could even sleep standing up, but that wasn't a skill I wanted to learn.

He woke, and realized after the fact that he could sleep standing up.

He wondered if he could sleep standing up, like a horse.

They were sleeping standing up, heads bowed, knees locked against their weight.

Meanwhile the others' eyes are near closed as they tries to sleep standing up.

Do you know how hard it is to sleep standing up?

He was so tired himself he could have slept standing up.

Some managed to sleep standing up, until the British artillery opened at 12oo hours.

"I get cold a lot faster, and I don't sleep standing up."