Spa Castle is like an amusement park - the admission price and the variety of offerings make it so that you want to spend the entire day there. Unlike most amusement parks, Spa Castle has a large number of vegan options. The food is pretty expensive (the salad bar is "pay by weight" and it's very easy to spend $12-$20 on a salad if you're not careful). I definitely wouldn't go out of my way to eat here, but it's a nice option if you're already planning a trip to Spa Castle.
Here are the vegan options offered at each station in the Food Court:
The Juice Farm features a number of fresh-squeezed juices and traditional Asian buns (the red bean buns and sweet potato buns are vegan). It also has some desserts that consist of red bean sorbet, ice and fresh fruits that are vegan.
Sushi Sushi has veggie sushi and edamame.
Little Italy serves pasta with marinara sauce (make sure that you specify "no cheese" if you are vegan).
The Salad Bar offerings vary, but it usually has oven roasted potatoes, seaweed salad, dairy-free pesto pasta (sometimes Spa Castle adds shrimp to it, so you need to check), beet salad, green bean salad and a selection of fresh fruits.
The 2nd Floor Starbucks has soy milk and can make any of its hot drinks dairy-free.