In a mixing bowl, whisk together soy sauce, brown sugar, pineapple juice, rice vinegar, garlic, ginger, black pepper, and salt to create the marinade.
Place the chicken breasts in a resealable plastic bag or a shallow dish and pour half of the marinade over the chicken. Seal the bag or cover the dish and refrigerate for at least 30 minutes or up to 2 hours for maximum flavor.
Preheat the grill to medium-high heat.
Remove the chicken from the marinade, allowing excess to drip off, and discard the marinade.
Place the chicken on the grill. Grill for about 6-8 minutes on each side, or until the internal temperature reaches 165°F (75°C).
Brush the remaining marinade onto the chicken during the last few minutes of grilling for added flavor.
Once cooked, remove the chicken from the grill and let it rest for a few minutes before serving.