In a bowl, mix together the cornstarch and flour. Dip the chicken pieces into the beaten egg, then coat with the cornstarch-flour mixture.
Heat the vegetable oil in a frying pan over medium heat. Fry the chicken pieces until golden and cooked through. Set aside.
In a separate pan, combine the rice vinegar, ketchup, brown sugar, soy sauce, and minced garlic. Bring to a simmer.
Add the pineapple chunks and diced bell peppers to the sauce. Cook for 5 minutes, stirring occasionally.
Add the fried chicken to the pan and toss to coat with the sauce. Cook for an additional 2 minutes.
Serve the sweet and sour chicken hot, optionally with steamed rice.