Rinse sushi rice under cold water until water runs clear, then cook in a pot with 1.2 cups of water. Bring to boil, reduce heat, cover and cook for 18 minutes. Remove from heat and let sit for 10 minutes.

Prepare seasoning by mixing 2 tablespoons of rice vinegar, 1 tablespoon of sugar, and a pinch of salt in a bowl. Microwave for 20 seconds until sugar dissolves, then gently fold into rice.

In a bowl, mix ¼ cup of mayonnaise, 1-2 tablespoons of sriracha, and 1 tablespoon of sesame oil. Stir in 1 cup of cooked shrimp and set aside.

Slice the avocado and cucumber into thin slices and strips respectively.

Assemble sushi stacks using a round mold, layering rice, avocado, spicy shrimp mixture, and cucumber, compacting each layer.

Remove the mold and garnish with sesame seeds, cilantro, and green onions. Serve immediately.