Prepare the Taco Shells:

Heat vegetable oil in a deep skillet over medium-high heat.
Fry the wonton wrappers or mini tortillas one at a time until crispy and golden brown, about 1-2 minutes per side.
Drain the shells on paper towels and set aside.
Cook the Sushi Rice:

Rinse the sushi rice under cold water until the water runs clear.
In a saucepan, combine the rice and water. Bring to a boil, then reduce the heat to low, cover, and simmer for 18-20 minutes until the water is absorbed and the rice is tender.
In a small bowl, mix the rice vinegar, sugar, and salt. Stir this mixture into the cooked rice and set aside to cool.
Prepare the Filling:

In a bowl, toss the diced sushi-grade fish with soy sauce, sesame oil, sriracha (if using), and sesame seeds.
Set aside to marinate while preparing the other toppings.
Assemble the Sushi Tacos:

Fill each crispy taco shell with a layer of sushi rice.
Add a few pieces of the marinated fish, followed by diced avocado, cucumber slices, shredded carrots, and green onions.
Garnish and Serve:

Top each taco with a drizzle of spicy mayo, a sprinkle of sesame seeds, and nori strips.
Serve with pickled ginger on the side, if desired.
Tips:

For a vegetarian version, substitute the fish with tofu or tempura vegetables.
Customize your tacos by adding other toppings like jalapeños, mango slices, or microgreens.
Enjoy your Sushi Tacos!