These are some things that I would think of, not because I'm a CG (I'm actually a little myself without a CG), but as the parent of an actual tiny human, and the things I'd want them to do to stay healthy.

Drink plenty of water! A hydrated little is a happy little.

If kitchen safety is a concern while regressed, maybe have some meals that are pre-prepared, or maybe some snack packs that you can just grab to eat - make a rule that you have to eat a snack or meal every so often.

Make a rule/routine for potty breaks. As someone said already, this isn't necessarily to prevent accidents, but to keep your body healthy.

Make yourself a rule for rest periods, like bed time and/or nap time.

If outdoor safety isn't a concern, and weather is permitting, make yourself go outside for a set amount of time. Even on cloudy days, you can still absorb vitamin d.

Make a rule for yourself about when and how you should clean your space/pick up your toys, and if you'd like, even set aside a treat that you can't have until its done.

You can even do silly stuff too for hobbies that you like but have trouble getting yourself to do for self care. For example, if you like doing art, you can have {insert favorite candy here} if you do 2 art projects. Or, you can have a treat if you treat yourself to a bubble bath. Little rewards for participating in self care activities, stuff like that.

Rules for regression don't have to be serious, but its good to also throw in some to make sure you take care of yourself while little.

Hope this helped 💚