I struggle with habits a lot, but this is one of the few that work for me. I think the kids call it "habit stacking"?

Basically, I have to brush my teeth and shower before going to bed. It's all one package, and I'm very efficient at it.

So it's at least once a day, more if I was sweating a lot.

Another one: brush teeth before leaving the house for the first time that day. ...that used to work better before working from home.

I've added a lot of other habits since then, using an overcomplicated system of deadlines and rewards.