Rice vinegar, or “su” (酢, す) is vinegar made from fermented rice. it’s a common ingredient in a variety of sauces, such as ponzu, and is used for flavoring sushi rice. As a result, it’s sometimes labeled as “sushi vinegar” as well as rice vinegar on the bottle.
It’s much less acidic than Western vinegar, so you really can’t substitute other vinegars for taste. Luckily, it’s easily available in grocery stores, so you shouldn’t have any trouble finding it.Buy on Amazon