Slice pork, bell peppers, and onion thinly.

Mix pork with 1/2 tbsp soy sauce and cornstarch.

Heat oil in a pan, sauté garlic and onion until fragrant.

Add pork and stir-fry until almost cooked.

Add bell peppers and stir-fry for 2 minutes.

Add remaining soy sauce, oyster sauce, sugar, and water.

Stir-fry until sauce thickens and everything is cooked through.