Prepare the Cucumber: Slice the cucumber in half lengthwise. Use a spoon to scoop out the seeds, creating two shallow boats. Pat the inside dry with a paper towel.
Add the Rice: Spoon cooked sushi rice into each cucumber half, pressing gently to create an even layer.
Add the Shrimp: Arrange 5–6 cooked shrimp on top of the rice in each cucumber boat.
Drizzle the Sauces: Drizzle unagi sauce and sriracha mayo generously over the shrimp.
Garnish and Serve: Sprinkle with sliced green onions and toasted sesame seeds. Slice into bite-sized pieces or enjoy whole. Serve immediately!