For the seasoning, heat the rice vinegar with the sugar and salt in a pot or microwave until fully dissolved.Rinse the sushi rice thoroughly and cook it in a pot with a thick bottom (or rice cooker).Once rice is ready, transfer to wooden or plastic container. Do not cover.Pour seasoning evenly over rice and mix with a wooden spoon in a cutting motion.Let rice cool down to room temperature by the window or with a fan, but never in the refrigerator.