The recommended ratio of water to rice is 1:1. This means that for every cup of sushi rice, you should add one cup of water. Place the rice in a microwave-safe dish, add the water, and cover it with a microwave-safe lid or plastic wrap. Microwave the rice on medium power for about 1-2 minutes per cup of rice. Check the rice after each minute and stir it to ensure even heating. The rice is done when it becomes soft and warm.