Texas man Shane Waldrop said he noticed the discrepancy after ordering a 20-ounce beer and a 24-ounce beer — equivalent to around 590ml and 710ml respectively.

Suspicious, he took the cups home and measured them both as being able to contain a maximum of 22 ounces each, or around 650ml.

Mr Waldrop’s class-action lawsuit against the Cinemark cinema chain alleges that it engaged in “deceptive and improper business practices”.

Attorney Jarret L. Ellzey said the company’s customers are “unwittingly overpaying for a supposed benefit they are not receiving”, FOX Business reports.