Preheat oven to 375 degrees F and prepare a muffin tin with non-stick cooking spray and set aside.
Ground and cook sausage in a skillet until fully cooked. Add garlic, peppers, and onions to the skillet and sauté with sausage for 2 minutes. Place this in your prepared muffin. Add chopped spinach into each muffin tin.
In a separate bowl whisk eggs with salt and pepper. Pour egg into each muffin tin filling about ¾ the way full. Top each one with cheese and bake for 20 minutes or until a fork can come out clean and eggs are cooked all the way through.