On a baking tray lined with parchment paper, split open the bagels and arrange cut-side up.
Spread two teaspoons of sauce on each bagel half.
Sprinkle the cheese evenly over each bagel half.
If using, sprinkle toppings of choice on each bagel, such as pepperoni or cooked sausage or vegetables, and press into the cheese.
Place the tray in the freezer until bagel halves are frozen, about four hours.
Remove the bagels from the freezer and arrange in a freezer-safe container or zip-top bag with pieces of parchment paper between each layer. Freeze until ready to use.
To cook, preheat toaster oven or conventional oven to 425 degrees F. Arrange desired number of pizza bagels on a tray lined with parchment paper. Bake until the cheese begins to brown, 12 to 15 minutes.