Combine oil, chile powder, paprika, coriander, oregano, cinnamon, cayenne, allspice, 3⁄4 teaspoon salt, and 1⁄2 teaspoon pepper in now-empty skillet.
Cook over medium heat, stirring constantly, until mixture is bubbling and fragrant.
Off heat, carefully stir in vinegar, sugar, and garlic (mixture will sputter). Let stand until steam subsides and skillet cools slightly, about 5 minutes.
Add pork to skillet. Mash and mix with rubber spatula until spice mixture is evenly incorporated into pork.