While no yogurt is sugar-free because of the natural sugars contained in lactose, some non-fat yogurt brands with minimal sugar include Danone Silhouette, Oikos 0% Greek yogurt, Chobani Simply 100 Greek yogurt and Fage Total 0. These products contain no added sugar or aspartame.
Danone Light & Fit, Danone Activia Lite and Blue Bunny Like 85 are non-fat yogurts that have added artificial sweeteners such as aspartame.
Greek yogurt tends to have less sugar content than regular yogurt, and plain varieties almost always have less sugar than their flavored counterparts. For a flavored yogurt, it is better to choose plain varieties and add toppings such as fresh fruit or honey at home.