Cut cod into thin strips (about 1/2 inch thick and 3-4 inches long.) Set aside. (Hint: partially thawed fish is much easier to cut than fully thawed fish.)
Mix flour, garlic powder, salt, and pepper until well mixed. Divide flour mixture evenly between two shallow bowls.
Mix egg and beer until well combined. Add to a third shallow bowl.
Pat a strip of fish dry with paper towels. Dredge in flour mixture of one bowl. Dip in egg mixture, and shake to remove excess. Dredge in second bowl. Place in prepared air fryer basket. Repeat with remaining fish. (Don't over-crowd the basket; work in batches if necessary.) Spray fish with cooking spray.
Set air fryer for 375. Air fry fish for 7 minutes or until golden.
Assemble Tacos
Warm tortillas in a skillet or in the microwave. Fill tortillas with cooked fish, and top with shredded cabbage, a drizzle of white sauce, and salsa. Squeeze limes over tacos, if desired.
Notes
Pre-shredded cabbage, such as from Trader Joe's, or even a coleslaw mix (not kit) would cut down a little on the prep for this recipe.