Bad taste following whipple

My dad (72M) had his whipple surgery 1 week ago. (Thursday) He started a full liquid diet on Day 4 post op, and has been cleared to begin eating normally on Tuesday (5 days post op).

He constantly has a bad taste in his mouth, as if he is belching rotten eggs/hospital fumes as he describes it. This killed his appetite.

He hates eating and has barely had 700 calories today. He feels full very quickly as well and doesn’t feel hungry.