Whisk the ingredients for the fish taco sauce together, then cover, and refrigerate.
Make the pico de gallo, shred the cabbage, and wash and chop cilantro leaves.
To make the fish tacos, start by slicing the fish into ¾-inch wide strips that are about 4 inches long (no need to be exact, but you don't want them much bigger than this). Pat the fish dry on all sides with a paper towel.
In a large bowl, combine the flour, breadcrumbs, baking powder, chili powder, cumin, salt, ancho chili powder, garlic powder, onion powder, cayenne pepper, egg, and ginger ale. Mix together to make a batter for the fish.
Add the strips of fish to the batter and use a spatula to gently stir it all to coat the fish evenly in the thick batter.
Pour enough oil into a large skillet to fill it about 1 inch deep, then heat it over medium-high heat to 375 degrees F. It is helpful to have a good candy thermometer to monitor the temperature of the oil.
When the oil is hot, add strips of the battered fish a few at a time, working in batches, and fry until golden brown, flipping the fish halfway through to cook evenly on both sides. Transfer to a cooling rack set over a paper towel-lined baking sheet.
Warm the tortillas in the microwave by placing a few at a time between damp paper towels and microwaving for 45 seconds, then repeating with the remaining tortillas until all are warmed. Keep them warm by covering them with a towel. Alternatively, you can fry the tortillas to warm them by heating a teaspoon of oil in another pan over medium heat, then frying each tortilla for 20 seconds on each side until it is soft and golden, but not crispy. You will need to add a little more oil after every other tortilla until you have warmed them all.
Assemble the fish tacos by adding the fish to two tortillas, doubled up. Then top with the shredded cabbage, pico de gallo, the fish taco sauce (I spoon it into a Ziploc bag and snip off the end so I can squeeze it on in squiggles), chopped cilantro, and sliced avocado, if desired. Serve with lime wedges for squeezing over the top.