Write a scene today about a character who has gone far too long without sleep. And not just in a ‘I went to bed too late last night’… make it a significant amount.
They say weird things happen when you’ve gone without sleep for too long. You start seeing things. Thinking in different ways. You lose inhibitions, and stop thinking as clearly as you vaguely remember being able to do.
Come up with any scenario that puts your character in this position, and just have fun with it.