For the quick-pickles: In a small saucepan, combine the vinegar, sugar, salt and 1/2 cup water. Bring to a boil, stirring to dissolve the sugar. Add the carrot and daikon and stir to combine. Turn off the heat and set aside to cool. Refrigerate, covered, for 2 hours.
For the sauce: Bring the soy sauce, brown sugar, mirin, vinegar and sambal to a simmer in a small saucepan. Cook for 5 to 7 minutes. Set aside to cool.
For the meatballs: In a large bowl, combine the chicken, panko, garlic, ginger, soy sauce, sesame oil, egg, scallions and some salt and pepper. Mix well to combine, but don't overwork. Form the mixture into eight 2-inch balls.
Heat a grill pan over medium-high heat. Drizzle the pan with canola oil. Add the meatballs and cook for about 4 minutes per side, or until cooked though. Baste generously with sauce during the last 3 minutes of cooking.
To assemble the sliders: Serve the meatballs on the buns, topping each with a tablespoon of the quick-pickles (drained) and some cilantro leaves. Secure with bamboo skewers and serve on a large platter with extra sauce on the side.