Hi @nancy 101,
Sue had a great suggestion in the comments here with honey. I might go a bit further and suggest Manuka honey as a stimulant for healing as well as soothing the throat. This honey is often quite thick so dilution with some warm water or tea would enable it to coat and soothe the throat from the radiation. Be aware of the healing properties of Manuka honey. It is a soothing remedy for cough that equals or surpasses some cough suppressants. The benefits likely outweigh the risks of the sugar consumed in this honey.

Lastly, back in 2008 I did research then and found in an England Journal of Medicine that honey could help soothe the throat. I did shots of real honey not the ones you find in your local grocery store which most are all synthetic and don’t have the same benefits. It definitely took some of the edge off for me. I would use Manuka honey which you can find on Amazon that scores at least UMF 10+ and MGO rating of 100+ are considered potent enough for medicinal use- the higher the rating, the more potent the benefits are, and of course, the more expensive, the honey.

In addition, I heard very good things about Red Light therapy, which uses infrared light from a wand in the throat has worked well for many. My current lymphoedema therapist where I am getting care now also is high on it including for lymphoedema which is another condition some patients will get.

Hope this helps and he will get better. Good luck on the journey.