For the sauce: Whisk the granulated sugar, vinegar, lime juice, fish sauce, garlic, and red pepper flakes together in a bowl; set aside for serving.
For the pork: Combine the Melt(R), fish sauce, soy sauce, brown sugar, garlic, and pepper in a bowl. Combine the marinade and pork in a large zipper-lock bag. Seal the bag tightly, toss to coat the pork, and let the pork marinate in the refrigerator for up to 1 hour.
Weave 2 pieces of pork onto each skewer.
For a Charcoal grill: Open the bottom grill vents completely. Light a large chimney starter filled with charcoal briquettes (100 briquettes; 6 quarts). When the coals are hot, pour them in an even layer over the grill. Set the cooking grate in place, cover, and heat the grill until hot, about 5 minutes.
For a gas grill: Turn all the burners to high, cover, and heat the grill until hot, about 15 minutes. (Adjust the burners as needed to maintain a hot fire.)
Clean and oil the cooking grate. Place skewers on the grill and cook until the meat is cooked through and lightly charred around the edges, 7 to 10 minutes, flipping the skewers halfway through.
Transfer the skewers to a platter and let rest for 5 minutes. Remove the meat from the skewers, sprinkle the cilantro leaves over the top, and serve, passing the sauce separately.
