Preheat the oven to 350°F.

In a large skillet over medium heat, cook the breakfast sausage until browned and fully cooked, breaking it apart with a spatula. Remove from heat and set aside.

In a bowl, whisk together the eggs, milk, salt, and pepper.

Pour the egg mixture into the same skillet and cook over medium-low heat, stirring gently until the eggs are just set but still slightly creamy. Remove from heat.

On a baking sheet, place the bottom halves of the mini bagels. Layer each with a portion of the cooked sausage, followed by a scoop of scrambled eggs, a slice of cheddar cheese, a few avocado slices, and a handful of spinach. Top with the bagel tops.

Bake in the preheated oven for about 10 minutes, or until the cheese is melted and the bagels are warm. Serve immediately.