Heat gas or charcoal grill. In medium bowl, mix apple, onions, poultry seasoning, salt and apple juice. Add ground chicken; mix well. Shape mixture into 4 patties, about 1/2 inch thick.
When grill is heated, carefully oil grill rack. Place patties on grill over medium heat. Cover grill; cook 14 to 20 minutes or until thermometer inserted in center of patty reads 165°F, turning patties once.
Spread honey mustard on bottom halves of buns. Top each with lettuce, chicken patty and top half of bun. If desired, serve with additional honey mustard.