What can be done for a dog for diarrhea?

you could try the following methods

Rice water: Boil high-quality rice in a lot of water, remove the grains, and offer the dog the creamy white soup that's left. ...
White rice.
Canned pumpkin (plain, not prepared pie filling) has the odd distinction of being effective for diarrhea and constipation.

Or you could try feeding it
cottage cheese, skinless, boiled chicken, and boiled, peeled potatoes.