Cut the chicken into strips.
Chop the pineapple and bell pepper into even cubes.
Combine 1 cup of water, pineapple juice, vinegar, and sugar in a pot. Warm the mixture over medium heat until it comes to a boil. Once boiled, cover the pot and take it off the heat.
Add 1 tbsp. cornstarch and ⅙ cup of water in a small bowl and whisk. Incorporate the cornstarch mixture into the pineapple mixture and continuously stir until it is slightly thickened.
In a wide bowl, combine flour, 1 tbsp. of oil, the remaining 1 tbsp. of cornstarch, egg, salt, and black pepper. Add 1 cup of water while whisking vigorously until you get a thick batter.
Add the chicken to the mixture and glaze.
Heat 2 tbsp. of oil in a shallow skillet. Add the chicken and fry until nicely golden.
After frying, remove the chicken from the skillet and transfer it to a plate.
Divide the cooked chicken, bell pepper, and pineapple onto serving plates.
Drizzle the hot sweet and sour sauce over.