Combine pineapple juice, brown sugar & soy sauce together thoroughly.
Place chicken breasts into a zipper bag.
Pour marinade over the chicken breasts in the zipper bag.
Allow chicken breasts to marinate for several hours in the refrigerator.
Flip the bag occasionally to allow for even marinating.
Heat your grill.
Place marinated chicken breasts onto the grill and cook until internal temperature reaches 165 degrees F.
Pull off the grill and let it cool before serving to kitty.