1. In a glass or plastic dish with a lid, combine the pineapple with its juice, soy sauce, onion powder, sugar, lemon juice, barbeque sauce, and curry powder. Taste, and adjust seasonings if desired. Place the chicken into the mixture, cover, and refrigerate for 1 to 2 hours.
2. Preheat an outdoor grill for medium-high heat. Place chicken breasts onto the grate, and grill until the meat is no longer pink inside. Brush occasionally with the pineapple sauce. Chicken should take about 7 to 10 minutes on each side.
3. Put the four cups water into a medium saucepan over medium-high heat. Add onions, celery, and rice. Bring to a boil, and reduce heat to medium-low. Simmer until rice is tender, about 20 minutes. In a separate pan, heat the marinade over medium heat until boiling. Simmer for about 5 or 10 minutes, then remove from heat, and set aside.
4. Serve the chicken on a bed of rice with the sauce covering it, or to the side.