> The food contains less than 0.5 g of sugars, as defined in § 101.9(c)(6)(ii), per reference amount customarily consumed and per labeled serving or, in the case of a meal product or main dish product, less than 0.5 g of sugars per labeled serving; and

>(ii) The food contains no ingredient that is a sugar or that is generally understood by consumers to contain sugars unless the listing of the ingredient in the ingredient statement is followed by an asterisk that refers to the statement below the list of ingredients, which states "adds a trivial amount of sugar," "adds a negligible amount of sugar," or "adds a dietarily insignificant amount of sugar;" and

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfr...

First, you can't add sugar, it has to be sugars that naturally occur in the other ingredients, but not ingredients that people know contain sugar like fruit, and second products don't have as much leeway as you think in defining their serving size. The FDA actually spells out what kinds of food get what serving size which is why you never see 1 chip / serving.