Sugar free is a descriptive term applied to certain manufactured foods. For packaged foods and drinks regulated by the U.S. Food and Drug Administration, sugar free is required to mean less than 0.5 grams of sugar per serving, and "contains no ingredient that is a sugar or generally understood to contain sugars."
Consumers should be cautious, however, especially of claims that are not regulated by the FDA. Numerous sweeteners that are not sugar but have the same calories and no meaningful health difference from sugar can be included in a product. Even FDA-regulated products are allowed to contain naturally high-sugar ingredients such as fruit juice.
In many cases, "sugar free" is a clue that sugar substitutes have been used in the formulation of a product.