1. Preheat grill to medium-high heat.
2. Place half of avocado in a bowl; mash with a fork until almost smooth. Add sour cream and next 3 ingredients to bowl; stir to combine. Dice remaining half of avocado. Add diced avocado, tomato, jalapeño, and 1/8 teaspoon salt to bowl; stir gently to combine.
3. Divide beef into 4 equal portions. Gently shape each portion into a (1/2-inch-thick) patty. Press a nickel-sized indentation in center of each patty. Sprinkle evenly with remaining 3/8 teaspoon salt and pepper. Place burgers on a grill rack coated with cooking spray. Grill 3 minutes on each side or until desired degree of doneness. Lightly coat cut sides of buns with cooking spray. Place buns, cut sides down, on grill rack; grill 1 minute or until toasted.
4. Place 1/4 cup sprouts on bottom half of each bun; top each with 1 patty, about 3 tablespoons guacamole, and top half of bun.