Combine first 9 ingredients in a large zip-top plastic bag; add pork. Seal bag and marinate in refrigerator 1 hour, turning occasionally.
Remove pork from bag, reserving 1/2 cup marinade. Thread 4 pork pieces, 4 pineapple cubes, and 2 onion pieces alternately onto each of 8 (12-inch) skewers. Place kebabs on grill rack coated with cooking spray; grill 10 minutes or until done, turning and basting occasionally with reserved marinade.