Bring the rice and water to a boil, reduce the heat and simmer, covered, until the rice is tender and the water has been absorbed, about 20 minutes, before letting it cool for a bit.
Gently fold the mixture of the rice vinegar, sugar, and salt into the rice.
Mix the avocado, cucumber, and lime juice together.
Mix the cooked shrimp, mayonnaise, and sriracha together.
Place the rice into the stack guides, pat down lightly, top with the avocado and cucumber mixture, followed by the shrimp mixture and a sprinkle of furikake.