Gently heat the vinegar, sugar and salt in a small pot or in the microwave and stir until sugar is fully dissolved.
Add freshly cooked rice to a bowl and pour in the seasoning mixture. Use a spatula or rice paddle to incorporate the mixture into the rice without breaking the rice grains.
Line the baking sheet trays with parchment paper and then transfer the seasoned rice onto the tray and gently press down to flatten until the rice is about an inch in thickness. Place the second sheet tray on top and press down, then toss into the freezer for 10 minutes or refrigerator for about an hour.
After chilling, remove the rice from the sheet trays and slice into nigiri sized rectangles.
Generously spritz or coat with neutral oil then pop into the air fryer at 375F or until crispy. Season with salt after air frying and set aside.