In a large skillet or wok, stir-fry pork in oil until no longer pink. Add garlic; cook 1 minute longer., In a small bowl, combine the soy sauce, sugar and ginger; add to skillet. Combine water and cornstarch until smooth; add to skillet. Bring to a boil; cook and stir until thickened, about 2 minutes. If desired, serve with rice and top with green onions and sesame seeds.