I have my kids always ask for the courtesy cup of water at pools, etc. Used to embarrass them at first, but now they willing do it so they can have cash for "better things."
We were just there last month. We would bring in 2 bottles of water with us to the parks, then just ask at any cart or restaurant to refill it with water. They would happily fill it for us. Very cold coming from the soda fountains! Much better and more refreshing than soda.