Cut the eggplants into 2" pieces. Heat the oil in a wok until shimmering. Add the chili and garlic and cook for 20–30 seconds. Remove the chili and reserve.
Add the eggplant and gently stir-fry. When the eggplant has soaked up all of the oil, add 1TB of the water. Keep adding water, 1TB at a time, until the eggplant is soft and you have used around half of the water.
Stir in the dark soy sauce and sugar then add the remaining water. Cover with a lid and cook for 1 minute. Remove the lid; the liquid should be absorbed. Return the chili to the wok, toss for 30 seconds and serve.