Rinse the sushi rice under cold water until the water runs clear.
Cook the sushi rice according to package instructions.
In a small bowl, combine rice vinegar, sugar, and salt; stir until dissolved.
Once the rice is cooked, mix it with the vinegar mixture gently.
Allow the rice to cool to room temperature.
Slice the cucumber lengthwise into thin strips.
Place a sheet of nori on a bamboo sushi mat, shiny side down.
Spread a thin layer of sushi rice over the nori, leaving a small border at the top.
Arrange the cucumber strips across the middle of the rice.
Roll the sushi tightly using the mat, applying gentle pressure.
Slice the roll into bite-sized pieces and sprinkle with sesame seeds if desired.