Using a spoon, melon baller, or potato peeler (like me!), cut a circle out of the top of the cupcake and scoop out some of the inside of the cupcake.
Cupcakes
Stuff the hole with sprinkles- pack them in there! (Or fill with filling like caramel or lemon curd!)
Sprinkles
Using your piping tip and bag full of frosting pipe on a huge swirl of frosting! I like to start in the middle over the hole, then in a spiral out and eventual up, apply the frosting.