Bring the rice to the boil with the water and salt, cover and simmer for 20 minutes; turn off the heat, fluff with a fork and let stand for a few minutes.
Heat the oil in a large, deep frying pan or wok over high heat.
Stir-fry in this order: first the chicken (tofu only at the end), then the onion and garlic, the peppers, the mushrooms and finally the pineapple.
Mix the cornflour with the pineapple juice and add to the pan with the teriyaki sauce; bring to the boil to thicken, thinning with a little water if needed.