Hi, my name is Stephen a retired pharmacist and a smoking quitter for 18 months.
I used to get sore spots and ulcers regularly after stooping cigarettes.
My son told me about nicotine replacement lozenges or gum which has to be taken every day but certainly made the ulcers go in time.
On holiday in Switzerland I could not buy the lozenges and was in pain over lunch.
The salad came with olive oil and wine vinegar, and when I tried the salad with the wine vinegar, my mouth smarted, but the pain went away as did the sores.
I do not know if wine or balsamic vinegar will help with mouth sores in cancer treatment, but it is not harmful or expensive and worth a try.
Wine or balsamic vinegar has a very bitter taste, but cured my sores for good. I take the vinegar twice a week as it gives you a nice energy lift and at first sight of any soreness of the tongue or mouth lining. but this is the only real help I have found.
I rinse the mouth with about 5ml of the vinegar then swallow ( you could spit it out if preferred)
Hope this helps! It would be nice to hear of anyone who tries wine vinegar for mouth sores.