Combine the pineapple juice, tomato sauce, soy sauce and garlic in a bowl. Add chicken and turn to coat. Cover and place in the fridge for 1 hour to marinate.
Thread the capsicum, shallot, pineapple and chicken alternately onto skewers. Spray lightly with olive oil spray.
Preheat a barbecue flat plate or a large frying pan on medium-high. Cook, turning occasionally, for 10 minutes or until golden. Serve.