In a mixing bowl, whisk together flour, cornstarch, baking powder, salt, and paprika.
Gradually add the cold sparkling water while whisking until you get a smooth batter.
Heat vegetable oil in a deep fryer or large pan to 375°F (190°C).
Dip the fish fillets into the batter, coating them evenly.
Carefully lower the coated fillets into the hot oil and fry for 4-5 minutes until golden and crispy.
Remove from oil and place on paper towels to drain excess oil.
Serve hot with tartar sauce and lemon wedges.