A Chicago-area Dunkin' customer has filed a proposed class-action lawsuit claiming the chain's Dunkin' Zero energy drinks aren't nearly as sugar-free as their name suggests. The complaint, filed by Illinois resident Phyllis C. Wells, alleges the lightly carbonated beverages contain significant amounts of a sweetener called allulose — a substance she says still counts as sugar under federal labeling rules, even though Dunkin' marketed the drinks as zero sugar.