Cook the Rice: Rinse the sushi rice under cold water until the water runs clear. Combine the rice and water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 18 minutes, or until all the water is absorbed. Remove from heat and let sit, covered, for 10 minutes.

Prepare the Sushi Vinegar: In a small saucepan, combine the rice vinegar, sugar, and salt. Heat over low heat, stirring until the sugar and salt are dissolved. Let cool slightly.

Season the Rice: Transfer the cooked rice to a large bowl. Gently drizzle the sushi vinegar over the rice, using a rice paddle or wooden spoon to carefully fold the vinegar into the rice. Be careful not to mash the rice. Allow the rice to cool to room temperature.

Cook the Shrimp: Heat the olive oil in a large skillet over medium heat. Add the shrimp, garlic powder, paprika, cayenne pepper (if using), salt, and pepper. Cook for 2-3 minutes per side, or until the shrimp are pink and opaque.

Make the Spicy Mayo: In a small bowl, whisk together the mayonnaise, sriracha, sesame oil, and soy sauce. Adjust the sriracha to your desired level of spiciness.

Assemble the Bowls: Divide the sushi rice among four bowls. Top with the cooked shrimp, diced avocado, sliced cucumber, and nori strips. Drizzle generously with the spicy mayo and sprinkle with sesame seeds.

Serve: Serve immediately, with optional toppings like pickled ginger, wasabi, or green onions.