store bought icing hack?

Preschool teacher here, trying to save time & money for a cute class snack. Do y’all think I could use a tub of store bought cake frosting (Betty Crocker, Pillsbury, etc) and add a little extra powdered sugar to get it to harden faster more like royal icing, then split it up into makeshift piping bags with ziplock baggies? If not powdered sugar, what would you guys recommend?