Peggy, I won't consider sleeping 16 plus hours a day to be normal after treatment even though extreme fatigue is inevitable. Dehydration can be a very serious problem and we surely need to drink a lot of water or other liquid to maintain our life at this point. How can your husband drink if he sleeps all day and night and so I suggest the best solution is to get him hospitalized for a few days for rehydration.
A curious point about weight loss. It seems that people on this forum lost a lot of weight after treatment. I told my oncologist about this and he was surprised at the great drop. He figured out it might be because western people are heavier than Asians. The normal range of weight loss among his patients is between 10 to 30 lbs. That's why when I lost 10 lbs, he admitted me to hospital for observation to find out if feeding tube was necessary for me. In the hospital I get treatment, an average of only 25% of head and neck cancer patients need to have a feeding tube during treatment.

Karen stage 4 tonsil cancer diagnosed in 9/01.