Reduce heat to medium. Add garlic, oyster sauce, soy sauce, sugar, and water directly to the pan. Toss everything together. The garlic will bloom in the sauce as it cooks. Stir and cook 2-3 minutes, tossing regularly, until the eggplant is completely tender and yielding when pressed with a spoon, silky inside and still holding its shape. The moment it starts collapsing pull it off the heat.