In a medium bowl, combine soy sauce, ketchup, apple cider vinegar, brown sugar, garlic powder, ginger powder, and a pinch of salt and pepper. Whisk until well blended.
In a large skillet or wok, heat vegetable oil over medium-high heat. Add the sliced beef and cook until browned, about 3-4 minutes. Remove the beef from the skillet and set aside.
In the same skillet, add the chopped onion and bell pepper. Stir-fry for about 2-3 minutes until they start to soften.
Add the pineapple chunks to the skillet and stir to combine. Return the beef to the skillet.
Pour the sauce mixture over the beef and vegetables. Stir well to coat everything evenly.
In a small bowl, mix cornstarch with 2 tablespoons of water to create a slurry. Add this to the skillet and stir until the sauce thickens, about 2-3 minutes.
Serve the sweet and sour beef over cooked rice.