It's always advisable to drink water throughout the day, whether incontinent or not. Dehydration from not drinking water is not fun and can cause everything from kidney stones, to constipation, to heart issues, etc.... As to how much, that really depends on you. I'm a huge water drinker. Always have been. The recommendation has always been 8 to 10 8 oz glasses of water per day, but you may find you need more, or you may find you need less.
A simple guideline I go by, is if my urine smells strong or the padding in my diaper looks like my urine is darker than usual, I'm no drinking enough. I don't know if this helps you or not, but that's the guideline that has always worked for me.
