I swear by my WaterPik water flosser. I had original Listerine to the water. Avoid using mouthwash with sugar in it as it can get in the tubes and cause mold. I use my water flosser daily when I have sores, otherwise, I use it about 3 times a week. It has cut down on mouth sores significantly and I don't have major dental issues. It really helps keep your gums clean.

I gargle with hydrogen peroxide but don’t swallow it!
Also use baking soda and water mixture helps too!

First, make sure your provider looks at them with a flash light. It could be from yeast or something else. Most oncologists have a solution called Magic Mouthwash. You can swish and swallow to help the sores and the pain. You also might need anti fungal or antiviral medication to help.

I love my WaterPik too!