This sweet and sour steak stir-fry is a delicious and flavorful dish that combines tender strips of beef with a tangy and sweet sauce. The steak is marinated in a mixture of soy sauce, ginger, and garlic, then stir-fried with colorful bell peppers, onions, and pineapple chunks. The sauce is made with a combination of vinegar, ketchup, brown sugar, and soy sauce, creating a perfect balance of flavors. Serve this stir-fry over steamed rice for a satisfying and easy weeknight meal.