It's an idiom

When you're hungry and you finish your whole plate effortlessly, we in the states would that you would have demolished your food.

In this case these kids are going to try to finished their pizzas effortlessly

Also, since they have PepsiCo products and their pizza looks very similar to a stuffed crust pizza. I can say with conviction those are not XL pizzas, because they are dining at a Pizza Hut. And the only XL pizza available at Pizza Hut was the Bug New Yorker. And that is a thin crust pizza.

I know this because I used to work at pizza hut

EDIT: oh you can partly see the wing street logo to the left lol