Cut the pineapple flesh in half through the center and then cut each half in two. Slice off the inner hard rind off the flesh and finally, cut each quarter into about 1-inch chunks. Store in the refrigerator till ready to use.

Combine pineapple juice, soy sauce, white wine vinegar, pressed garlic, sliced onion, garlic salt, powder, onion powder, and brown sugar in a bowl and whisk well. Cut boneless, skinless chicken thighs in half and add it to a large zip-lock bag. Pour 2/3 of the marinade into the bag, close it well, and lay the bag on a large plate. Place chicken into the refrigerator to marinate overnight (or for at least 2 hours). Refrigerate the other 1/3 marinade - in a container separate from chicken - store in the refrigerator.

Spray each skewer with some cooking oil spray all around and place skewers onto the grill grate. Cook the skewers turning them a quarter of the way every 4-5 minutes. Cook till the chicken is 165° internally.

Simmer the remaining 1/3 of the chicken marinade that you set aside on stove-top until reduced by half. Brush chicken kebabs with some of the sauce and enjoy!