Make the fish: Preheat oven to 375°F.
Spread the coconut on a rimmed baking sheet and bake until lightly toasted, about 5 minutes. Scrape into a shallow bowl and let cool. Add the breadcrumbs, cumin, garlic powder, and chili powder and season with salt and pepper.
Spread the flour in a second shallow bowl and season with salt and pepper. In a third shallow bowl, lightly beat the eggs.
Line a rimmed baking sheet with parchment paper and lightly grease with nonstick cooking spray. Pat the fish dry with paper towels and season with salt and pepper. Working with a few pieces of fish at a time, dredge in flour, tapping off any excess. Dip the fish in the eggs, letting any excess drip back into the bowl. Coat the fish in the coconut mixture, pressing to adhere. Arrange the breaded fish on the prepared baking sheet and repeat with the remaining ingredients. Bake the fish until golden brown and cooked through, 12 to 15 minutes. Sprinkle the fish lightly with salt.
Meanwhile, prepare the tacos: In a small bowl, whisk the mayonnaise with the lime juice. Season with salt and pepper. In a large bowl, toss the jicama with the fennel, fennel fronds, cucumber, serrano, and cilantro leaves. Pour some of the dressing over the vegetables and gently toss to coat. Season the slaw with salt and pepper.
Fill the corn tortillas with 1 to 2 pieces of fish and top with a generous pile of the slaw. Garnish with pineapple, avocado, and small cilantro sprigs. Serve right away, passing lime wedges and hot sauce at the table.