My husband really struggled with dehydration and weight loss as well. For him I think it was a combination of many things- exhaustion, nausea, loss of appetite, change in taste. He also had extremely high output which wasn't controlled despite many adjustments in diet and medications- even specialized injections which sadly were ineffective. His change in mood was no doubt a result of the physical challenges and emotional confusion too. He noticed an improvement when he became willing to take the anti-nausea medicines that were prescribed for him. This allowed him to eat a bit more and gain some strength. He became disgusted at the thought of more Gatorade or other electrolyte drinks. I found online an electrolyte replacement tablet. You swallow it as a pill. We showed it to both his oncologist and surgeon who didn't really have an opinion on it. They couldn't approve/endorse it but didn't discourage it either. He decided to take it and it made a noticeable improvement in his fatigue. My suggestion would be to discuss how you're feeling (every last bit of it) to your team of doctors. They can then present you with options to best support you during this process and they will know what will be safe and healthy for you to pursue.