Place the sushi rice in a fine-mesh strainer and rinse under cold water until the water runs clear.
Combine rice and water in a rice cooker or a medium saucepan. If using a saucepan, bring the mixture to a boil over medium-high heat, then reduce the heat to low, cover, and simmer for 18-20 min until rice is tender and the water is absorbed. Place a metal sheet pan in the freezer to cool.
In a small saucepan, combine the rice vinegar, sugar, and salt. Heat over low heat, stirring occasionally, until the sugar and salt dissolve completely. Remove from heat and let it cool to room temp.
Gradually add the seasoning to the rice, gently folding in.
Transfer to cooled sheet pan and spread in a thin layer to cool. Bring to room temp. Wet your hands. Separate into 1/2 cup-1 cup portions into patties. Flatten. Store in fridge or freezer.