Just a point that may be of interest to some, there is a dry mouth prescription med ( spray ) which is called Glandosane.
Your docotr must specify which flavour when writing the script…so choose peppermint or lemon ( the neutral is disgusting imo )
It is nearly £10 to purchase over counter.
Handy for keeping in handbag/pocket when you may not have water to drink.
Ell