Preheat your oven to 350°F and lightly grease a 12-cup muffin tin.
Heat a skillet over medium-high heat and cook the sausage until browned. Add the finely chopped bell pepper and onion, then sauté for 3-5 minutes, or until the vegetables have softened and any excess moisture has evaporated. Remove from the heat and let cool slightly.
In a large bowl, whisk together the eggs, egg whites, milk, hot sauce, garlic powder, onion powder, salt, and pepper until well combined.
Stir in the chopped spinach, Parmesan cheese, and the cooked sausage and vegetable mixture. If you'd like, reserve a small amount of the sausage mixture to sprinkle on top before baking.
Evenly divide the mixture between the prepared muffin cups, filling each about three-quarters full. Sprinkle the tops with a little extra Parmesan cheese.
Bake for 22-25 minutes, or until the egg bites are fully set and the tops are lightly golden.
Let cool for a few minutes before removing from the muffin tin. Serve with sliced avocado, hot sauce, and fresh fruit for an easy, high-protein breakfast. Enjoy!