This is sort of a tough question. I tend to agree with Costello that it generally doesn't matter, but some people use this question to determine cultural fit, which can be very important some places. On that note, I completely agree with PityOnU, no company wants you to tell them why they are awesome, they all ready know this. They are trying to determine how well you will fit in to the culture. The important things to discuss in answer to this question is what experience you have that will provide benefit to them, and what in particular they have that will make you passionate about your job and allow you to grow. An employer likes to hear that there is something unique about them that will encourage you to work harder.
Here are a couple examples:
My sister is studying business and applying for a role as a sales person at a clothing boutique. She can honestly say that her academic background in sales and marketing will help her to sell products to customers, and she can gain real world experience in an area that she is passionate about, clothing and shoes.
I studied computer science, with a decent background in graphics and systems design. I worked at medical imaging company and when I applied, I discussed how my skills could help to develop their products, and how I was interested in the medical field because I felt that it has an important impact on peoples lives.
In your case, you could talk about how your experience in retail food could help your perspective employers, and if there is something unique about the food they serve, how you are interested in learning more about. e.g. it is a Mexican restaurant, and you are interested in expanding your experience in cooking Hispanic foods.
You still want to be honest though, and ideally there is something about this place in particular that is appealing to you (maybe it is the only decent restaurant is a small town, and that is a fine reason too), but if the answer is simply that you need a job and you think that they are the best fit and that you would enjoy working there more than anywhere else, than that is a perfectly valid answer. However, interviewers tend to be decent at picking up on bullshit, so don't give a bullshit "I love this restaurant, it's the best" sort of answer (especially if that isn't the case).
In the end though, I suspect with this sort of job application that there is some practical component, such as cook this dish and we will taste it (for programming jobs there is always a decent amount of programming). These sort of practical components are way more important than any individual verbal response, so don't sweat it too much. Work experience is also a really important factor in job applications, generally more so than interviews. If you can give eloquent succinct answers to the verbal questions though, it can definitely give you an edge over other applicants, as regardless of the job, employers are always looking for intelligent and competent employees.
