This is a standard question in any drunk driving case. The police suspect you have, and they want you to help out by confirming it. Don't do it!
Although there may be an issue as to whether a Miranda warning should precede such a question, it is still one that induces you to incriminate yourself. By saying "yes," you are basically testifying against yourself. You are confessing to drinking and driving!
So what do you do? Smile politely and say, "I am exercising my right to remain silent." This is a response to the question that asserts your rights and does not give away anything (other than the smell of alcohol on your breath, but that's a whole other problem!)
The officer might respond that you are not under arrest (only important as to whether he must read you your rights) or imply that if you haven't been drinking, you have nothing to hide, but stick to your guns. Repeat the response until he moves on.
If you have been charged with drunk driving in southern New Jersey, please feel free to call me at 856-432-4113 or contact me through this site to schedule a free consultation.
If you are looking for more information on New Jersey's drunk driving law, then download my free book, How Much Trouble Am I In? A Guide to New Jersey Drunk Driving Law.