In a medium bowl, combine diced mangoes, finely diced red onion, chopped fresh cilantro, minced jalapeño, and lime juice. Add a pinch of salt and toss until mixed. Set aside.

In a large mixing bowl, whisk together all-purpose flour, chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Gradually mix in cold beer or sparkling water until a smooth, thick batter forms.

Heat vegetable oil in a deep pot or frying pan to 350°F (175°C). Ensure the oil is the right temperature for frying.

Dip pieces of firm white fish fillets into the batter, ensuring they are coated. Fry in batches for 3-4 minutes per side until golden brown and crispy. Transfer to a wire rack to drain.

Warm corn tortillas in a dry skillet over medium heat for about 30 seconds on each side until pliable and slightly toasted.

Fill each warm tortilla with a piece of crispy fish and top with mango salsa. Serve immediately.