In a shallow glass dish, mix the soy sauce, brown sugar, sherry, sesame oil, ginger, and garlic powder. Stir the chicken pieces and pineapple into the marinade until well coated. Cover, and marinate in the refrigerator at least 2 hours.
Preheat grill to medium-high heat.
Lightly oil the grill grate. Thread chicken and pineapple alternately onto skewers. Grill 15 to 20 minutes, turning occasionally, or until chicken juices run clear.