The food was good, typical barbecue stuff. You will see some of the dining room servers working on CC too, serving lunch.
I don't know where to find a menu, but the foods I remember are hamburgers, hot dogs, grilled chicken sandwiches, potato salad, watermelon, soda, and I think there are lobster burger sandwiches too, maybe only over at the adult beach.
I think the only food/beverage not included while on
Castaway Cay are alcoholic drinks.
EDITED TO ADD:
I just found the activities sheet from our CC day last year, and here is what it lists: COOKIES BBQ 11:30am - 2:00pm "Hamburgers, cheeseburgers, BBQ ribs, lobster burgers, chicken sandwiches".
Parrot Cay is open 12:00pm - 1:30pm