01 - Crumble breakfast sausage into a large skillet over medium heat. Cook until browned and cooked through, about 6 to 8 minutes. Transfer to a plate and set aside.
02 - In the same skillet, cook 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 tortillas flat on a work surface. Evenly divide the egg and sausage mixture among the tortillas, then top each with shredded cheddar cheese.
05 - Fold in the sides of each tortilla and roll up tightly. Let cool slightly, then wrap each burrito individually in foil or parchment paper. Place in a freezer-safe bag or container.
06 - From frozen, remove foil, wrap in a paper towel, and microwave on high for 2 to 3 minutes. Alternatively, bake at 350°F for 25 to 30 minutes until heated throughout.