Rinse sushi rice under cold water until the water runs clear, then combine with water in a rice cooker or saucepan and cook.

Once rice is cooked, mix rice vinegar, sugar, and salt in a small bowl until dissolved, then fold into the rice.

Chop cucumber and avocado into desired shapes and set aside.

Layer sushi rice into serving bowls, top with cucumber and avocado, and add crab or tofu.

Drizzle soy sauce and sriracha over each bowl.

Serve immediately while rice is warm.