I don't think there is anything you can use QS credits for. You can use snack credits. Outside the stadium, there are places you can use QS credits for.
In the stadium they have "snack" food. Popcorn, Caramel Popcorn, Cotton Candy, Churros, Nachos, Fruit, Almonds, Pretzels, Chips, Ice Cream (Mickeys Bars, Ice Cream Sandwiches) Bread Cones, Drinks.
Most things are Snack Credits except the Hot Dogs, Bread Cones, Popcorn in the Souvenir Buckets. There is also a small selection of alcohol that you can't use snack credits for.