Whisk the sugar, soy sauce, onion, garlic and black pepper together in a large bowl. Add the pork and toss to coat. Cover and refrigerate at least 2 hours. Overnight is best if possible.
Preheat an outdoor grill for high heat, and lightly oil the grate.
Thread the pork onto the soaked skewers. Cook on the preheated grill until the pork is no longer pink in the center, 3 to 5 minutes per side.
