Prepare the batter: In a bowl, mix flour, paprika, garlic powder, salt, and black pepper. Gradually whisk in beer or sparkling water until smooth. Let it rest for 10 minutes.

Make the slaw: Combine shredded cabbage and julienned carrot in a bowl. In a separate bowl, mix mayonnaise, sour cream, and lime juice. Toss half of this dressing with the cabbage mix.

Cut the cod: Pat the cod fillets dry and cut into 1-inch thick strips. Season lightly with salt and pepper.

Fry the cod: Heat oil in a deep pan to 350°F (175°C). Dip each cod piece in the batter, letting excess drip off, then fry for 3-4 minutes until golden brown. Drain on paper towels.

Warm tortillas: Heat a dry skillet over medium heat. Warm each tortilla for about 30 seconds per side until pliable.

Assemble tacos: Place 2-3 pieces of fried cod on each tortilla. Top with slaw, avocado slices, and cilantro. Drizzle with remaining lime crema. Serve with lime wedges.

Serve immediately while the fish is still hot and crispy for the best texture and flavor.