In a small saucepan, combine half of the jalapeno, 1 tablespoon vinegar, 1 tablespoon sugar, the ketchup, orange juice, soy sauce and hoisin sauce. Bring to a simmer over medium heat and cook for 10 minutes.
Meanwhile, in a medium bowl, toss together the coleslaw mix, remaining 1/4 cup vinegar, remaining 3 tablespoons sugar and 1/2 teaspoon salt. Let stand at room temperature, tossing occasionally, for 20 minutes.
Preheat the grill to medium. Season the pork tenderloins generously with salt and pepper, place on the grill, cover and cook, turning once or twice, until seared all over, about 5 minutes. Brush with the sauce and cook, basting occasionally, until the pork registers 140 degrees ; on an instant-read thermometer inserted in the thickest part, 6 to 8 minutes. Place on a cutting board and let rest for 5 minutes; slice thinly. Stir the remaining jalapeno and the cilantro into the coleslaw and serve with the pork.