Chop the pineapple, chicken, onion and sweet red peppers. Mix together the water, vinegar, sugar and corn starch.
Heat the oil in a cook pot and fry the onion and the chicken until golden.
Add the pineapple and the sweet red peppers - heat for about 3 minutes.
Stir the liquid ingredients, add to the cook pot, and bring to a boil. The cornstarch will thicken and the sauce will coat all ingredients.
Serve plain, with rice or rice noodles.