Suggestions for a DnD Club at my school

So a few of my friends are planning to start a DnD club at my high school, and I want to help them come up with activities. I don’t think it’s feasible to be able to run a full blown, high commitment campaign since people come and go, have other clubs, etc. Plus after school activities usually go on for onky an hour or so.

Basically what are some recommended low commitment and short dnd sessions/concepts?