Creating Sweet and Sour Fish is a straightforward process. Follow these simple steps to achieve delicious results:

1. Prepare the Fish: Rinse the fish fillets under cold water and pat them dry with a paper towel.
2. Season the Flour: In a shallow dish, mix the flour, salt, and black pepper. Dredge each fish fillet in the seasoned flour, ensuring they are evenly coated.
3. Heat the Oil: In a large skillet, heat the vegetable oil over medium-high heat. Once hot, carefully add the floured fish fillets to the pan.
4. Fry the Fish: Cook the fish for about 3-4 minutes on each side, or until golden brown and cooked through. Remove the fish from the skillet and place them on a paper towel-lined plate to drain excess oil.
5. Sauté the Vegetables: In the same skillet, remove excess oil, leaving about 1 tablespoon. Add the sliced bell pepper and onion. Sauté for 2-3 minutes until they are slightly tender.
6. Prepare the Sauce: In a bowl, mix the sugar, vinegar, ketchup, and soy sauce. Pour this mixture over the sautéed vegetables. Stir well and cook for another 2-3 minutes until the sauce thickens slightly.
7. Thicken the Sauce: In a small bowl, mix the cornstarch with water to create a slurry. Add this to the sauce mixture, stirring continuously until it thickens to your desired consistency.

Once the sauce is ready, return the fried fish to the skillet, ensuring they are well coated with the sweet and sour sauce.