Slice the sweet onion into 1/2-inch thick rings and cut the chicken breast into thin, even strips.
In a medium bowl, whisk together the flour, light beer, egg white, garlic powder, paprika, sea salt, and black pepper until a smooth, bubbly batter forms.
Dip each onion ring and chicken strip into the batter, ensuring they are fully coated, and let any excess batter drip off.
Arrange the coated pieces in a single layer in the air fryer basket, ensuring they do not overlap.
Mist the tops lightly with avocado oil spray to enhance the crispiness.
Air fry at 375°F for 10-12 minutes, flipping halfway through and spraying again, until the coating is golden brown and the chicken is cooked through.
While the rings and chicken cook, whisk the Greek yogurt and lemon juice together in a small ramekin to create a bright dipping sauce.
Serve the crispy onion rings and chicken hot with the lemon-yogurt dip on the side.