In a medium mixing bowl, combine soy sauce, brown sugar, pineapple juice, ketchup, rice vinegar, minced garlic, grated ginger, sesame oil, black pepper, and crushed red pepper flakes (if using).

Whisk everything together until the sugar is fully dissolved and the mixture is smooth.

Pro Tip: Whisk continuously to make sure the brown sugar dissolves completely—this helps the marinade coat the chicken evenly without gritty spots.

Using a sharp knife, cut the chicken thighs into evenly sized 1.5-inch cubes. This ensures they cook evenly on the grill.

Chop the bell peppers and onion into similar-sized pieces, about 1.5 inches each.

Cut fresh pineapple into chunks roughly the same size as the chicken and veggies to keep cooking times consistent.

Place the chicken cubes into a large resealable plastic bag or shallow dish.

Pour half of the prepared marinade over the chicken, reserving the other half for basting and glazing later.

Seal the bag or cover the dish and refrigerate for at least 2 hours, ideally 4–6 hours for maximum flavor.

Pro Tip: Marinate longer but no more than 8 hours—pineapple juice contains enzymes that can make the chicken mushy if left too long.

If using wooden skewers, soak them in water for 30 minutes to prevent burning.

Thread the marinated chicken, bell peppers, onion, and pineapple chunks alternately onto each skewer, leaving a little space between pieces for even cooking.

Place the assembled kebabs on a plate or tray while you heat up the grill.

Preheat your grill or grill pan to medium-high heat (around 375°F to 400°F).

Lightly oil the grill grates using a folded paper towel dipped in oil and held with tongs. This prevents sticking and helps with grill marks.

Place the kebabs on the hot grill and cook for about 4–5 minutes per side.

During the last few minutes of grilling, brush the reserved marinade generously on each kebab to build up a sticky, flavorful glaze.

Turn the skewers carefully using tongs to avoid losing any pieces.

Continue grilling until the chicken reaches an internal temperature of 165°F and has a nice charred look.

Remove the kebabs from the grill and let them rest for a couple of minutes.

Serve hot with your favorite sides like steamed rice, grilled veggies, or a fresh salad.

Don’t forget to spoon any extra glaze left on the grill over the kebabs for that final burst of flavor!