In a small microwave-safe bowl, warm the grape jelly for about 15 seconds, then whisk in the BBQ sauce and apple cider vinegar until smooth. Set aside.
Preheat the air fryer to 390°F for 3 minutes. Meanwhile, slice the kielbasa into 1/2–3/4 inch medallions if not already prepped.
Arrange the kielbasa in a single layer in the basket (use a perforated air-fryer parchment liner if you want easier cleanup). Air fry for 4 minutes.
Flip or shake the basket. Brush or toss the kielbasa with half of the sauce, then air fry for another 3–4 minutes, until the edges brown and the glaze bubbles and lightly caramelizes.
Transfer the hot bites to a clean bowl, add the remaining sauce, and toss to coat. Let rest 2 minutes so the glaze sets, then serve with toothpicks.