I also had dry mouth and drank glass after glasses of water it even woke me up, I found it was worse with my first round of chemo 5FU, Epirubicin and Cyclophosamide. I also ended up with mouth sores so I brushed my teeth gently with warm water and baking soda and my onco gave me nystatin to swish and swallow it really helped. But the dry mouth is just an indicator that water is constantly drank. It's important to the bladder as the chemicals can cause a bladder infection if you don't keep it full. When they switched me to Docetaxel that went away but then had and still have lots of bone and joint pain and brown fingernails
Good luck