you need to tell me what you mean by sick? does he feel nauseated, vomitting or constipation? what is the stage of his cancer?
there are medicines to solve all the three problems i have mentioned above. try to give him as much of fliuds as possible to keep him hydrated, cook his favorite food. give him soft diet
. this is as much i can say from the information that you have given me.
if you have any more questions feel free to contact me