Begin by thoroughly rinsing sushi rice under cold water until the water runs clear. In a rice cooker, combine rinsed rice with water, and cook according to manufacturer's instructions.

Transfer the cooked sushi rice into a bowl, adding rice vinegar, sugar, and salt while warm. Gently fold to combine and allow to cool to room temperature.

While the rice cools, slice cucumber into thin strips and dice the avocado, setting aside until ready to assemble.

In serving bowls, start with a scoop of seasoned sushi rice as the base. Layer on cucumber slices and diced avocado, then add your choice of protein.

Combine soy sauce with sriracha in a small bowl. Drizzle over each assembled bowl.

Serve immediately while the rice is still warm and the vegetables remain crisp, optionally with pickled ginger and wasabi.