Mix soy sauce, oil, sherry, brown sugar, and garlic in a medium bowl. Pour into a large resealable bag. Place chicken in the bag, and shake to coat. Marinate in the refrigerator for at least 4 hours.
Preheat an outdoor grill for high heat and lightly oil the grate.
Place chicken on the prepared grill. Cook until no longer pink in the center and juices run clear, 6 to 8 minutes on each side. Discard remaining marinade.
Chicken Marinade · Dinner Match Lab | Dinner Match Lab