Ahoy, Cindy!
You are a girl after my own heart! While I appreciate that there is unlimited soda at the beverage stations, I typically drink brewed iced tea and water. After 12 Disney Cruises, I am an EXPERT on the iced tea situation onboard.
The bad news is that the beverage station does not have brewed iced tea. For quite awhile, it was Nestea, which IMHO was not even worth drinking. The iced tea at the beverage station is now Fuse. This is still not brewed, nor is it great. So, I have a couple of options for you.
First of all, in Enchanted Garden in the morning, they have a breakfast buffet. You sit at a table and a server brings your drinks. You can order brewed iced tea here. If you bring a large Tervis cup or water bottle, your server will happily bring you multiple teas to fill it. Brewed tea is also served in Royal Palace at breakfast and lunch, but this is an entire sit-down restaurant for each meal.
Secondly, the beverage station has tea bags and hot water. You could make a cup of hot tea, fill your large bottle with ice and pour the tea in. I'm sure you would have to make a couple of cups this way, but it would work in a pinch.
At dinner, you can always get brewed iced tea in all of the main dining rooms, so once again, bring that big cup or bottle to fill up. It takes a little strategic planning, but it is available and can be done.
I hope this helps with your cruise planning! Please visit the Disney Parks Moms Panel with more cruise questions as they arise!
Happy Crusing, Tracy V.