Preheat the oven to 375°F (190°C). Grease a standard 12-cup muffin tin with non-stick spray or line it with paper liners.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, garlic powder, Italian seasoning, and salt until well combined.
In a separate bowl, whisk together the eggs, milk, olive oil, and pizza sauce until smooth.
Pour the wet ingredients into the dry ingredients and stir gently with a spatula until just combined. Do not overmix; a few small lumps are perfectly fine.
Fold in the mozzarella cheese, Parmesan cheese, mini pepperoni, and any optional vegetables until evenly distributed throughout the batter.
Divide the batter evenly among the 12 muffin cups, filling each about ¾ full. Sprinkle the tops with extra mozzarella, mini pepperoni, and a pinch of Italian seasoning.
Bake for 18–22 minutes, or until the tops are golden brown, the cheese is bubbly, and a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool slightly.
Serve warm with pizza sauce for dipping, or allow them to cool completely before packing them into lunchboxes or storing them for later.