Heat your air fryer to 400°F (200°C) and let it warm up for about 3 minutes to get the basket hot and ready.
Pat the bratwurst dry with a paper towel after removing them from packaging to reduce moisture for better browning.
Spritz each brat lightly with olive oil spray to help them brown evenly in the air fryer.
Arrange the brat links in a single layer in the basket, making sure they have space to let air circulate around them.
Cook the brats for 8 minutes, then listen for the sound of sizzling to check they’re cooking well.
Turn each brat over carefully using tongs to expose the other side to direct heat.
Continue cooking the brats for 7 more minutes until the skins become crispy and golden brown.
Check that the internal temperature has reached 160°F (71°C) by inserting a meat thermometer into one of the links.
Remove the brats and let them rest on a plate for 3 minutes to let the juices settle inside.
Open the brioche rolls and spread stone ground mustard evenly, then add the air-fried brats and top each with sauerkraut and caramelized onions before serving.
