Just buy a liter, and use the old "if I don't drink it, it will go bad" line. You can also pretend to use it for marinating a steak, but need the obligatory "sample" while you do your marinating. The "marinating" ploy actually isn't even a falsehood. You ARE marinating something. Of course, that "something" is YOU.
I'm divorced, so I moved myself up from 2 glasses per day. It was a good trade. Rotten wife for good wine.