Coat a non-stick skillet with non-stick spray; heat over medium. Add the sausage, onion, red pepper, and sweet potato and cook, covered, stirring often, until vegetables are tender (test a chunk of sweet potato to be sure).

Meanwhile, beat eggs with milk in a small bowl until blended. When the vegetables are tender, transfer them to a plate. Return the skillet to the burner, add the egg mixture and cook, stirring often, until eggs are softly scrambled.

Off heat, stir in spinach, reserved sausage mixture, salt, and pepper. Serve immediately with a toasted English muffin half.