Hi there, Lara!
What a healthy drink your daughter loves! Like you, I would keep encouraging that excellent habit.
Most of the table service and character dining locations do offer tomato juice as a beverage option. It will likely be a challenge to find tomato juice at quick service locations.
You can confirm in advance by checking out the menus on the
official Walt Disney World dining page, or by visiting the menu section on AllEarsNet.com, a fan site that is unaffiliated with Walt Disney World.
Remember, too, that Disney allows Guests to bring in food and beverage, provided the containers are not made of glass. You are more than welcome to bring in a cooler full of chilled juice, the brand that is most to her liking.
Have a happy, healthy visit!
See you later, celebrator,
-Deborah B.