Heat oil in a wok on medium-high fire. Add in garlic and onion, and stir-fry over medium heat until fragrant, about half a minute. Add in sambal belacan and sugar, and stir-fry for another minute.
Add in kangkong, stems first. Stir-fry for a few seconds, then add in the leafy parts. Over high heat, stir-fry quickly to make sure all the greens are in contact with the heat.
Add in water for some gravy. To retain its fresh look and crunch, you want to work the spatula quick and cook the greens not more than two minutes. As soon as the leaves turn just wilted, turn heat off and dish out quickly.
Squeeze in some lime juice and garnish with red chili peppers.