Cut the pork into bite-sized pieces.
Slice the onion, green onion, and garlic.
Mix soy sauce, sugar, water, and pepper to make the marinade.
Place the pork in a pan and stir-fry.
Add the onion, green onion, and garlic and stir-fry together.
Pour in the marinade and simmer over low heat.
Finish when the sauce is reduced.