Combine first 6 ingredients in a small bowl, stirring with a whisk.
Heat a medium nonstick skillet over medium-high. Divide and shape sausage into 4 (3-inch) patties. Add patties to pan; cook 3 minutes on each side or until browned and done. Remove patties from pan; keep warm. Add spinach to pan; cook 1 minute, stirring until wilted.
Spread mayonnaise mixture evenly over cut sides of English muffins. Top bottom halves of muffins evenly with patties, spinach, apple slices, and top halves of muffins.