When we travel by air we each have a bottle of water.
We just kept refilling that from the tap on the ship. It tasted as good as the drink station water.
I guess some have specific likes and dislikes, but we found no reason to carry on anything more, or to buy the soda passes on board for the kids. I left it up to the kids, and they were perfectly happy with soda at dinner, and the free lemonade,milk, water, hot chocolate at the beverage station. My son did accidentally get a glass of half-and-half instead of milk, said it was the best glass of milk he had ever had!!!