Here is the suggestion my sister gave for mouth sores caused by Sutent:
Sores in the mouth
1/2 teaspoon of baking soda and 1/2 teaspoon of salt in 8 oz of warm water rinsing your mouth 4-5 times a day.
I havent had a need to use it but she said the doctors she works with prescribe it to Sutent patients where she works.
Let me know if it works for you. I havent had a need to use it myself.