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