Dungeons and Dragons

Alcohol poisoning - drank too much the night before and can't face the day. They'll catch up later!

If you must have them with the party you could run them in a supportive role and simply buff the party where possible (bless, guidance) and keep them off the front lines.

If the players trust each other enough you could have one of them run the character in a similar way to lighten your load.

Beyond that others have suggested good ideas: shopping, a job from their holy order, helping someone in town are always classics.

You could perhaps have the guard arrest them for something and have a jail break as well 🤣

I don't have a fun and entertaining way, but I wanted to put in two cents anyway. My husband DMs frequently, and regularly has players miss sessions. Life gets in the way, whatever, no biggie. He always explains players being gone as a story that is told long after it happened - different people remember things slightly differently, sometimes they remember certain important figures being there and sometimes they don't. They might even argue about it, ten years down the line. To him, every session is just another chapter in a story, told by imperfect people with imperfect memories.