With sharp knife, cut sweet potatoes into strips three or four inches long and 1/4-inch thick. Line baking sheet with aluminum foil or parchment paper, and spread fries on it in one layer. Spray them lightly with cooking spray. In small bowl, stir together seasoning and sugar. Sprinkle this mixture on fries, tossing gently. Bake at 350° 45 to 55 minutes, until fries are soft. Serve with dipping sauce. Serves 4.