There is no direct prohibition to consume food products until they are paid for in the Law "On the Protection of Consumer Rights" (https://zakon.rada.gov.ua/laws/show/1023-12#Text). However, until the customer pays for the product, it is the property of the supermarket. Employees can only make a remark and ask to pay for it at the cash register. If the buyer refuses to pay, they can call the police.