Work your own schedule apps?

I know there’s Uber eats and waitr, but are there other apps that let you work whenever you want? I think there’s a pet sitting app but I can’t think of the name.

I want to be able to work some while in In school and maybe this summer, but I have a month long trip coming up and an 18 hour semester this fall. I know a lot of jobs aren’t looking for that kind of gap.

What do y’all do to make extra money?