Make the base: In a heat-safe, oven-safe dish that fits your air fryer basket, whisk together pineapple juice, vinegar, ketchup, brown sugar, soy sauce, garlic, and ginger.

Preheat the air fryer: Set to 350°F (175°C) for 3 minutes to warm the basket. This helps the sauce heat evenly.

Start the sauce: Place the dish in the basket and air fry at 350°F for 6–8 minutes, stirring once midway. The mixture should be hot and starting to steam.

Mix the slurry: In a small bowl, whisk cornstarch with water until smooth. No lumps.

Thicken it: Carefully remove the dish, whisk in the slurry, and return it to the air fryer. Cook 3–5 more minutes, stirring once, until the sauce looks glossy and coats a spoon.

Adjust and finish: Taste and tweak. Add a pinch of salt if needed, more sugar for sweetness, or a splash of vinegar for brightness. For heat, stir in chili flakes or a bit of sriracha.

Optional veggies: If using bell pepper or onion, stir them in with the slurry and cook until slightly tender but still crisp, about 4–5 minutes.

Serve: Use immediately as a dip, drizzle, or toss with air-fried chicken, tofu, or shrimp. It will thicken a bit more as it cools.