Place the rice in a bowl and gently rinse with cold water three or four times. Transfer to a strainer and let it rest for about 20 minutes.
Heat the vinegar, sugar, and salt in a nonreactive pan over medium heat, stirring until the sugar and salt are dissolved. Set aside.
Place the rice and 1 1/2 cups of water in a saucepan. Simmer, cover, and cook over very low heat until the rice is tender and the water evaporates, about 20 minutes. Remove it from the heat, and let it rest, covered, for 20 minutes. Transfer the rice to a bowl, and toss with the vinegar mixture.
For each serving, spoon a 1/2 cup of rice into a small cylindrical container lined with plastic wrap. Turn the rice onto a plate, remove the wrap, and smooth the rice.