Roll the mashed potatoes into strips, dip them in beaten egg, coat with flour, and fry until golden brown. Similarly, coat the shrimp meat with batter and fry until cooked. Set aside.
Heat some oil in a pan, stir-fry minced garlic, onion, and green and red bell peppers until fragrant. Add the sweet and sour sauce, bring to a boil, thicken with cornstarch slurry, then add the fried shrimp meat and potato strips. Quickly stir-fry until everything is well coated, then serve.