Everyone makes mistakes; no one is perfect. The interviewer knows that too and is asking this question to see how you handle situations when you make mistakes. Give an example that demonstrates how you took responsibility for your error and fixed it. Also, include what you learned from the experience as a result. Sometimes learning from our mistakes allows us to gain some valuable tools.
"When I first started my current job, I was a bit overwhelmed with the variety of drinks our customers ordered. One day, I mixed up three orders in a row. It wasn't because I didn't know how to make the drinks. It was because I wasn't actively listening, due to nerves. I made a Caf? Mocha instead of a Caf? au lait. Then, a Frappuccino instead of a Caramel Macchiato. I apologized profusely and quickly repaired the situation by making the correct drinks and offering to pay for the ones I made in error. Now, I am sure to actively listen to every customer as they place their specific orders."
"Luckily I have never mixed up an order related to a food allergy; however, in my first year as a server, there were a couple of instances where I forgot how a customer wanted their steak done or the accompaniments they chose. I started to write down my orders, and then as I learned the menu and gathered memorization and recall techniques, I was able to better rely on my memory. Of course, when I have mixed up orders in the past, I assume the blame, apologize, and repair the situation as soon as possible."