Rinse the sushi rice in a fine-mesh strainer under cold water until the water runs clear. Combine the rinsed rice and 2 cups of water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 18-20 minutes. Remove from heat and let it sit, covered, for 10 minutes. In a small bowl, whisk together rice vinegar, sugar, and salt until dissolved. Gently fold the vinegar mixture into the warm rice using a rice paddle or spatula. Spread the rice on a baking sheet to cool to room temperature.

While the rice cooks, prepare all toppings. Shred or chop the imitation crab into bite-sized pieces. Julienne or dice the cucumber. Julienne or shred the carrot. Slice the avocado. Thinly slice the green onions. Cut the nori sheets into thin strips or small squares using kitchen shears.

In a small bowl, whisk together the mayonnaise, sriracha, sesame oil, and soy sauce until smooth. Taste and adjust spiciness by adding more sriracha if desired. Set aside.

Divide the cooled sushi rice evenly among four bowls. Arrange the imitation crab, cucumber, carrot, and avocado in neat piles or sections on top of the rice. Drizzle generously with the spicy mayo. Sprinkle with toasted sesame seeds, nori strips, and green onions. Add a small pile of pickled ginger to the side of each bowl. Serve immediately with lime wedges on the side.