Dissolve the sugar in the vinegar, then add the shredded cabbage and grated carrot. Mix and refrigerate.

Dice the tomato and onion into small cubes, and finely chop the serrano pepper. Mix together, season with salt, and refrigerate.

Blend the mayonnaise, chipotle pepper, and sour cream. Season with salt and garlic powder, then refrigerate.

Thinly slice the red onion and marinate it with lime juice (or white vinegar) and salt. Let it rest in the refrigerator for at least 2 hours.

Warm the tortillas before serving.

In a bowl, mix the egg yolks, beer, salt, pepper, and 2/3 cup flour until you have a smooth batter.

Beat the egg whites until stiff peaks form, then gently fold them into the batter. Add oregano and mustard, and set aside.

Cut the fish fillets into strips, coat them in the 3 tablespoons flour, then dip them in the batter.

Fry the fish in oil heated to 340°F (170°C) until golden brown. Drain on paper towels.

Serve the fried fish in the tortillas with the prepared toppings.