For The Dressing: Whisk together vinegar, fish sauce, sugar, lime juice, garlic and red pepper flakes in small bowl; set aside.
To make the meatballs, mix the pork, one tablespoon of sugar, black pepper, soy sauce, minced garlic and salt. Form into small meatballs.
Heat a frying pan and brown the meatballs. When they are fully browned, remove from the pan. Don't clean out the pan. In the same pan, add the remaining 2 tablespoons of sugar and the remaining 1/4 cup of water. Stir to dissolve, then allow it to cook on high without stirring until it becomes very browned and bubbly. This is caramel. Add the final 1 cup of water and stir to combine. Return the meatballs to the pan and cook in the caramel sauce for 15 minutes, stirring occasionally to coat.
Meanwhile, chop the peanuts, cilantro, cucumber, scallions and lettuce. Grate the carrots with a box grater.
Place the noodles in large flat bowls first, arrange the meatballs along with the rest of the ingredients around the noodles in the bowl. Serve with Sriracha.