In a large mixing bowl, combine the shredded green and purple cabbage alongside the chopped cilantro, lime juice, mayonnaise, honey, and a pinch of salt and pepper. Toss everything together until well mixed and the ingredients are coated. Allow the slaw to chill in the fridge while you prepare the fish, letting the flavors meld.

In a separate bowl, whisk together the sour cream, mayonnaise, lime juice, garlic powder, cumin, and salt. This tangy sauce will not only complement the fish but also bring a lovely creaminess to your tacos. Make sure the mixture is smooth and well blended, then set it aside.

Combine the cornstarch, flour, garlic powder, paprika, salt, and black pepper in a large bowl. Gradually whisk in the cold sparkling water until the batter achieves a smooth, somewhat thick consistency. It should be bubbly from the sparkling water, which will help achieve that perfect crunch.

In a deep frying pan, heat your vegetable oil to approximately 350°F (175°C). Once hot, dip the fish fillets into the batter, ensuring they are thoroughly coated. Carefully place the battered fish into the hot oil, frying them until golden brown and crispy, about 3-4 minutes each side. Once cooked, transfer the fish to a plate lined with paper towels to drain excess oil.

Warm your tortillas in a dry skillet or microwave until soft. Lay them out on a serving platter and ready to assemble. Start with a generous layer of cilantro lime slaw as the base, followed by pieces of the crispy fish. Drizzle the creamy sauce over the top before adding any optional toppings, like avocado slices or pickled onions, for extra flavor.

Garnish your tacos with extra chopped cilantro and serve them with lime wedges on the side. Encourage your guests or family to squeeze fresh lime juice over their tacos to heighten the flavors.