In May, we did not have bottled water in the room but, there was always cold water in a pitcher. They sell two sizes in the store. The smaller size is what I would buy in any gas station/vending machine here and it was $1.00. I don't know how much the much larger size was.
Yes, bring an insulated water cup/jug. They do not have bottled water to keep everything clean and "green". There is water from the fountain machines. I'd also recommend the fruit infused water at the beach bar (self-dispensing), it's very tasty and refreshing!
We were at CN the first week in May and there was no bottled water. You could get cups of plain water at the bars or they had self-serve flavored water that you could fill cups with at the bar near the beach grill.
no bottle water at CN unless you want to pay for it in the gift shop. There are water coolers in breakfast area, and jugs of fruit flavored in the beach bar. Bring your insulated water cups -- you can use them for bar drinks too.