I wanted to add something to the comment that Whozit made about Blizzard Beach. They do offer the $9.99 refillable mug. They also have a program that if you bring your hotel refillable mug to the park, you can pay $5 for a sticker that has the bar code on it and get unlimited drinks for that day.
We just happen to find this out because I was drinking out of my cup when we were walking into the park and one of the CM's caught me and asked if I wanted to purchase the $5 sticker. Typhoon Lagoon is probably on this program also.
Hope this helps!
Michelle