1. In small bowl, stir together mayonnaise, ketchup, relish, sugar, dried onion and salt. Cover and refrigerate until ready to use.Burgers:
2. In large bowl, mix together sirloin, Worcestershire, salt, pepper and garlic powder. Form into 6 hamburgers, about 3/4 inch thick.
3. In large skillet, cook bacon over medium-high heat until crisp, 6 to 8 minutes. Remove to paper toweling to drain; keep warm.
4. Prepare outdoor grill with hot coals or heat gas grill. (Or cook using oven method, below.) Grill burgers, uncovered, 4 minutes. Turn over; grill 3 minutes or until internal temperature registers 155 degrees F on instant-read thermometer. Place a slice of cheese on each burger. Grill, covered, 1 minute, until cheese melts. Remove burgers from grill; keep warm.
5. Toast the buns if you wish.To construct burgers:
6. Reserve 6 bun tops. Spread each bun bottom with 1 tablespoon sauce. Place a burger on top of each of 6 bottoms. Top each with one of the remaining bun halves; spread each with 1 tablespoon sauce. Arrange 2 strips cooked bacon and 1 lettuce leaf on each. Top each with one of reserved bun tops. Serve with remaining sauce, and with French fries, if desired.