Make fries: Preheat oven to 425°F. Line a large baking pan with foil; mist foil with cooking spray. In a large bowl, toss sweet potatoes with oil, sugar, cumin, cayenne, 1/2 tsp. salt and 1/4 tsp. pepper.
Set potatoes in a single layer on baking sheet. Bake until lightly browned around edges, about 15 minutes. Turn potatoes; bake until softened and browned, about 20 minutes longer. Sprinkle with additional salt and pepper.
Make burgers: Preheat broiler to high or grill to medium. Line a broiling pan with foil and mist with cooking spray.
Pulse beans with 2 Tbsp. water in a food processor until blended. Transfer to a bowl; add sirloin, salt and pepper. Gently blend and shape into four round, flat patties.
Broil or grill burgers until a meat thermometer registers 160°F, about 5 minutes per side. Serve burgers with lettuce and tomato on toasted English muffins, with fries on the side. Offer ketchup, mustard and other condiments, if desired.
