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 diced red bell pepper and yellow onion until softened, about 4 to 5 minutes. Add 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 over the vegetables. Scramble gently over medium-low heat until eggs are just set. Remove from heat and fold in the cooked sausage.
04 - Lay tortillas flat on a work surface. Divide the egg and sausage mixture evenly among the tortillas. Top each portion with shredded cheddar cheese.
05 - Fold in both sides of each tortilla, then roll up tightly from the bottom to seal. Allow burritos to cool slightly before wrapping.
06 - Wrap each burrito individually in foil or parchment paper. Place wrapped burritos in a freezer-safe bag or airtight container and freeze until needed.
07 - 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.