In a medium bowl, mix together shrimp, mayonnaise and sriracha. Set aside.

In a another small bowl, mash the avocado with salt and pepper. Set aside.

In a third small bowl, combine the cooked rice with soy sauce and rice vinegar. Set aside.

Spray a 1 cup dry measuring cup with cooking spray. Layer half the shrimp mixture, half the cucumbers, followed by half the mashed avocado and finally half the rice mixture.

Carefully turn the cup upside down to turn the stack out onto a plate, lightly tapping the bottom of the cup if necessary. Repeat with the remaining ingredients to make a second stack. Sprinkle with sesame seeds and serve immediately!