How to Make It
Stir together ketchup, brown sugar, 1 tablespoon pineapple juice, and 1 tablespoon vinegar in a small bowl. Set aside.
Combine pork, 1/4 cup scallions, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a medium bowl; form into 8 patties. Spray a large cast-iron skillet with cooking spray, and heat over high. Add patties, and cook until slightly charred, 2 to 3 minutes. Flip and cook until pork is cooked through, about 1 minute. Transfer to a plate.
Add pineapple slices to skillet, and cook on 1 side until lightly charred, 1 to 2 minutes. Top patties with pineapple slices.
Combine cabbage, remaining 2 tablespoons pineapple juice, remaining 1 tablespoon vinegar, remaining 1/4 cup scallions, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper in a bowl. To assemble sliders, brush bottoms of rolls with ketchup mixture; add a pork patty with a pineapple slice to the bottom of each bun. Top with cabbage mixture and tops of rolls.