Your relationship is doomed
If you are looking for savage comebacks and responses then search for Wendy’s Twitter account which is supreme in the business. They always have a precise recipe of irony and publicity when they are giving answers. Their public relations team is ultimate in this kind of thing.
In this situation, a customer asked for advice from them. But due to sarcasm, the customer ended up knowing the harsh reality. Though they are funny in the end it’s a restaurant, pal. Consult your friends for advice.