01 - In a large skillet over medium heat, crumble and cook the breakfast sausage until browned and cooked through, about 6 to 8 minutes. Remove sausage to a plate and set aside.
02 - In the same skillet, sauté bell pepper and onion until softened, about 4 to 5 minutes. Add chopped spinach and cook until wilted, about 1 minute.
03 - In a mixing bowl, whisk together eggs, milk, salt, and pepper. Pour into the skillet with vegetables. Scramble gently over medium-low heat until eggs are just set. Remove from heat and stir in cooked sausage.
04 - Lay tortillas on a flat surface. Evenly divide the egg mixture among tortillas, top each with shredded cheese. Fold in the sides and roll up each burrito tightly.
05 - Allow burritos to cool slightly. Wrap each burrito individually in foil or parchment paper, then place in a freezer-safe bag or container.
06 - Remove foil, wrap in a paper towel, and microwave on high for 2 to 3 minutes from frozen, or bake at 350°F for 25 to 30 minutes until hot throughout.