In a medium bowl, whisk together yogurt and sugar until sugar dissolves. Taste and add more sugar if you like.
Spoon mixture into an ice cream maker and freeze according to manufacturer's directions. Transfer yogurt to a container and freeze until firm, about 2 hours.
Make ahead: Freeze up to 1 week. Let soften at room temperature about 45 minutes before scooping, or microwave a few seconds until softened.
Note: Nutritional analysis is per 1/2-cup serving.