In a medium bowl, combine the vinegar, sugar, and ¼ teaspoon salt, stirring until the sugar dissolves.
Add the cucumbers and jalapeño and let sit, tossing occasionally, for at least 5 minutes.
Meanwhile, heat the oil in a large skillet over medium-high heat.
Cook the pork, breaking up with a spoon until no longer pink, 5 to 6 minutes. Stir in the hoisin sauce, ginger, and 2 tablespoons water.
Fill the pita halves with the pork and the cucumber salad.