Changes in saliva are stopping my partner from sleeping

1. My partner is just about to begin his fifth week of six in radiotherapy for tonsil and one lymph node SCC. He has also been hospitalised with pneumonia, (he got out a week ago,) and has injured his shoulder. He is understandably pretty tired. He is taking in only four fortisips a day, and tea.

Yesterday the changes in saliva began and he seems to be producing large amounts of sticky goo. The only way he can deal with this is to cough it up and spit it out. He has to do this every few minutes, and of course, this wakes him up. How have you all coped with this?