Combine the oyster sauce, sugar, sesame oil, and water in a bowl. Stir. Set aside.

Combine oil and garlic at the same time in a pan. Turn the heat to on. Cook the garlic in medium heat until it starts to turn light brown.

Pour the oyster sauce mixture in the pan and sprinkle some ground black pepper. Stir. Let boil.

Add the bok choy. Stir and cover. Cook until the sauce reduces to half. You may add some salt if needed.

Transfer to a serving plate. Serve with rice. Enjoy!