Cut the chicken breasts into small, bite-sized pieces.

Place the chicken pieces in a bowl.

In a separate bowl, combine 2 tablespoons of soy sauce and 1 tablespoon of cornstarch to create a marinade.

Pour the marinade over the chicken pieces and stir to coat evenly.

Prepare the sweet and sour sauce: In a bowl, combine 2 tablespoons of chopped tomatoes, 2 tablespoons of white vinegar, 1/2 tablespoon of soy sauce, 1/2 tablespoon of cornstarch, and 2 tablespoons of powdered sugar.

Set the sauce aside.

Peel the yellow and red peppers, removing the seeds.

Cut the peppers into small cubes.

Heat a frying pan or wok over medium-high heat with 1 tablespoon of oil.

Brown the marinated chicken pieces in the hot oil until cooked through.

Remove the chicken from the pan and set aside.

Add the remaining 1 tablespoon of oil to the pan.

Fry the cubed peppers over low heat until they are tender, approximately 5-7 minutes.

Add the cooked chicken back to the pan with the peppers.

Drain the pineapple chunks from the can of pineapple juice, reserving the juice if desired.

Add the drained pineapple chunks to the pan with the chicken and peppers.

Pour the prepared sweet and sour sauce over the mixture in the pan.

Mix well to combine all ingredients.

If the sauce is too thick, add a little water or some of the reserved pineapple juice to achieve the desired consistency.

Cook for about 15 minutes, stirring occasionally, until the sauce has thickened and the flavors have melded.

To serve, sprinkle the sweet and sour fried chicken with sesame seeds.

Serve hot with cooked white rice on the side.