Heat half the oil in a wok or large frying pan over high heat. Add half the chicken and stir fry for 2-3 minutes or until well browned. Transfer to a plate and repeat with remaining chicken.
Heat remaining oil in wok over medium heat. Add pineapple, onion, capsicum and beans and stir-fry for 2-3 minutes.
Combine arrowroot with a little vinegar. Add to the wok with the remaining vinegar, sugar, soy sauce, and chicken. Toss for 1-2 minutes or until the sauce comes to the boil and thickens slightly.
Serve the sweet and sour chicken with the rice. Sprinkle with sliced green shallots, if desired.