Combine first 3 ingredients in a large heavy-duty, zip-top plastic bag. Add fish; seal bag, and shake until fish is well coated. Marinate in refrigerator 1 hour, turning occasionally.
Remove fish from marinade, reserving 3 tablespoons marinade. Discard remaining marinade. Combine reserved marinade, brown sugar, honey, and oil in a small saucepan. Cook over medium heat until mixture comes to a boil and sugar dissolves.
Coat grill rack with cooking spray; place on grill over medium-hot coals (350° to 400°). Place fish on rack. Grill, covered, 4 to 5 minutes on each side or until fish flakes easily when tested with a fork, basting occasionally with brown sugar mixture. Garnish with flowering chives, if desired.