Look I'm in pain and this concept sounds fun.
Fairly simple, take AUs and put your characters in them,
Also, I find this exercise good for fleshing out characters for some reason, maybe it's putting their personality through a different scenario to see other sides you missed or whatever
Some common AUs include-
- Coffee Shop AU
- Doctor AU (My favourite)
- Fantasy AU
- Paitent AU
- Some variant of soulmate AUs.
I'll post an example :) xx