Prepare the Marinade: In a bowl, combine ketchup, brown sugar, soy sauce, pineapple juice, olive oil, rice vinegar, garlic, ginger, sesame oil, salt, and pepper. Mix well to create a sweet and savory marinade.

Marinate the Chicken: Add the chicken cubes to the marinade, ensuring each piece is well coated. Cover and refrigerate for at least 30 minutes.

Preheat the Grill: Preheat the grill over medium-high heat and brush the grates with olive oil.

Assemble the Kebabs: Thread the marinated chicken, fresh pineapple, green peppers, and red onion onto skewers, alternating ingredients.

Grill the Kebabs: Cook the skewers on the grill for 10-15 minutes, turning occasionally, until chicken is cooked through.

Serve Immediately: Remove from heat and serve hot.