Heat the oil in a wok or frypan over high heat. Add the eggplant and stir the eggplant until soft, about 4 minutes.
Stir in the water, dried chilli flakes and garlic. Cover and simmer until all the water is absorbed. Meanwhile, mix sugar, cornflour, soy sauce and oyster sauce together in a bowl until sugar and cornflour have dissolved. Stir sauce into the eggplant, making sure to evenly coat the eggplant. Cook until the sauce has thickened.