Prepare a bowl of cold water to wet your hands. (This will prevent the rice from sticking to your fingers)
For sushi rice:
Dissolve the sugar in the rice vinegar.
In a fine mesh strainer, rinse the rice under running water until the water is clear.
In a saucepan, weigh the rice and add 1.5 times its volume in water.
Bring to a boil and cook for 15 minutes over low heat, covered. Let the rice cool down.
Pour the sugar-vinegar mixture over the rice and mix with a bamboo spatula.
Spread a bamboo mat or a plastic food wrap on a work surface.
Place a thin, even layer of rice on the surface.
Cut the nori sheet.
Place the cucumber pieces lengthwise.
Roll everything up, closing the roll.
Refrigerate until serving.