1. Combine first 11 ingredients in a large zip-top plastic bag. Add swordfish steaks; seal bag, and shake until steaks are well coated. Marinate in refrigerator 2 hours, turning bag occasionally.
2. Prepare grill.
3. Remove steaks from marinade, reserving marinade. Place marinade in a small saucepan. Bring to a boil; boil 1 minute.
4. Coat grill rack with cooking spray. Place on grill over medium-hot coals (350° to 400°). Place swordfish steaks on rack; grill, covered, 3 to 4 minutes on each side or until fish flakes easily when tested with a fork, basting occasionally with marinade. Garnish swordfish steaks with fresh basil sprigs, if desired.