Rinse your mouth with a combo of salt, baking soda and water. Recipe is aporx 16 oz qater, 2 tsp of baking soda and 2 tsp salt. If it burns decrease the amount of salt or even omit it. Rinse at lease 5 times per day more is better.

Before you eat or drink swish the magic mouthwash in your mouth for several seconds, then spit it out. It should calm your mouth enough to get you thru eating and drinking.

Unfortunately, the mouth sores are a very unpleasant part of rads. Do the best you can with keeping up with rinsing and magic mouthwash. Push yourself to get minimum 48 oz water in per day and 3000+ calories. If you arent able to do that then a PEG tube would be the practical solution. Its not anything most of us wanted to get but it is something that is a tremendous help in keeping your nutrition and water consumption where it should be. Even with a peg tube make sure you still swallow water every single day. Also you need to stretch your mouth open as wide as possible to avoid other problems later.

Best of luck with your treatments.