It's good they found out about being dehydrated. When you're feeling badly it's hard to be able to keep track of how much water. Maybe lining up some water bottles for the day so he knows how much more he has to go to complete his required water intake. Sometimes you have to try different things until you find what can be tolerated. Certain meds can cause unexpected reactions. When my son had a lot of nausea, his meds had to be switched. It can be pretty depressing to feel badly for what seems so long. If the oncologist can be involved he may have some suggestions that could really help get your husband back on tract and feeling better. Hope things improve a lot very soon!