Waiters must be pleasant and have great communication skills, as the job involves talking to people from all walks of life, often for hours on end. Being a waiter can be stressful, especially when there are a lot of people; it's important to be able to multitask while remaining pleasant and in a good mood. You must convince your potential employer that you really like people and that you know how to show elegance in the face of pressure. Unfortunately, I don't know why you left your last job. Or if you've ever had a last job.
Or if you sell crack and are looking for a second job. I have no idea, but whatever you did or were doing before coming here to apply for this job, you have to be prepared with a good story and an explanation of why whatever you were doing is no longer the path you wanted to follow and why this path is the best since the Bourne Identity movies. Does it make sense? But as I always tell my students, memorize the drinks I offer at TheRealBarcourse. I have the 101 most common cocktails and the 21 most ordered drinks.
You only need to memorize about half of them to get started, and you'll be fine. If you do, you'll be easily prepared for this question. If you're not a TheRealBarCourse student, try to find and memorize the 50 best drinks you can find and you won't have a problem.