Preheat the oven to 425 degrees F. Line a rimmed baking sheet with parchment paper or a Silpat.
Place the bagels, cut side up, onto the prepared pan. Top with pizza sauce, using about ¼ cup on each. Spread it to the edges of each bagel half.
Top with cheeses and any desired optional toppings.
Bake for 8-10 minutes, or until cheese is melted and lightly browned.
Remove from oven and let cool for a minute or so before cutting and serving.
Notes
Store any leftovers in an airtight container and reheat in the microwave or toaster oven until warmed through.
To freeze a batch, prepare as directed and let cool fully on the pan or on a wire rack. Place in a single layer in a freezer bag, remove as much air as you can and freeze.
To warm from frozen, place frozen pizza bagels on a baking sheet lined with parchment paper and cook for 4-6 minutes in a 375-degree-F oven or toaster oven, or for about 30-60 seconds on a heat-safe plate in the microwave.
Cut up for younger kids—they may be easiest for 1-year-olds to chew if cut into thin strips.