In a medium-sized bowl, whisk together gochujang sauce, soy sauce, sesame oil, vinegar and sugar.
Pour into a resealable plastic bag. Add the tenderloins and squish the bag to mix ingredients. Marinate in the refrigerator for at least 1-2 hours.
Preheat grill to medium-high heat. Remove pork from marinade (reserving marinade) and grill for 15-25 minutes, turning occasionally with tongs.
Cook until the internal temperature reaches 160°F in the thickest part. Remove from grill and let rest for 10 minutes.
While pork is resting, pour marinade into a saucepan and bring to a boil over high heat.
Boil for a minimum of 5 minutes, reduce heat, and simmer until thickened slightly, coats the back of a spoon, and has a glaze-like appearance.
Slice pork and serve over cooked rice. Drizzle sauce over the top and garnish with scallions, fresh herbs and sesame seeds. Serve extra sauce on the side.