1) For the marinade: Combine the sugar and vinegar in a small saucepan. Cook over medium heat, stirring occasionally, just until the sugar melts. Remove from the heat and stir in the chili sauce and salt. Cover and refrigerate until needed.
2) In a medium bowl, combine the cucumbers, onion, and pepper. Add just enough marinade to cover the vegetables, stir, and chill for 1 hour before serving. Garnish with fresh mint or cilantro and chopped peanuts if desired.