Final answer:
The nurse should advise the woman not to restrict her fluid intake despite the side effect of dry mouth from the antispasmodic medication, as hydration is essential for bladder health.
Step-by-step explanation:
The nurse's best response to the client who experiences dry mouth as a side effect of an antispasmodic for overactive bladder syndrome and is afraid to drink water would be "You shouldn't restrict your fluid intake because it will only make your bladder problems worse." Antispasmodics can cause dry mouth by affecting the autonomic nervous system's regulation of salivation, which might dissuade someone from drinking enough fluids. However, maintaining proper hydration is vital for overall bladder health and to avoid further complications. Strategies such as using products like Biotene to relieve the symptoms of dry mouth may also be beneficial.