Waitrose has begun asking customers to make a purchase before being entitled to a free hot drink in its stores.
The supermarket said it was trialling the purchase requirement to find out how the offer was being used by its six million myWaitrose cardholders.
Two branches began the trial at the end of September with seven more joining last week.
A Waitrose spokesman said it had not been decided how long the trial would last and there were no plans to roll it out to any more branches.
“Our myWaitrose free tea and coffee offer is one of the ways we thank our customers for shopping with us - and we want all our customers to be able to enjoy a free hot drink when they shop with us in our branches,” he said.
“The trial in nine of our shops simply asks customers to confirm they’ve made a purchase before picking up their free coffee. There’s no minimum spend for this purchase.”
Recently, Twitter has seen a number of comments from shoppers frustrated by queues for the free tea or coffee offer in busier Waitrose stores and machines breaking down or running out of milk.
The nine branches involved in the trial are Billericay, Mountsorrel, Bury St Edmunds, Leigh-on-Sea, Norwich, Swaffham, Southend, Hawkhurst and Clifton.
The spokesman added that so far the vast majority of customers in the nine branches had given positive feedback about the trials.