In 1-gallon bag, combine chicken with soy sauce, water, sesame oil, brown sugar, garlic and onion. Marinate in refrigerator about 4 hours.
Heat grill to medium heat.
Prepare rice according to package directions, replacing 2 cups water with coconut milk.
Once finished marinating, remove chicken and pat dry. Grill about 7 minutes per side, or until internal temperature reaches 165 F.
Pat pineapple rings dry and grill about 1 minute per side.
Mix shredded coconut with rice. Place pineapples on top of chicken and serve with rice.