Seen in a British supermarket (Sainsbury’s, Lancaster in northwest England) in May 2008:
Hmm, isn’t vinegar an uncountable/noncount/mass noun? So why the plural –s marker?
That’s because it’s not the substance that is being referred to here, but specific varieties thereof: indeed, on the shelves we see balsamic vinegar, white balsamic vinegar, red wine vinegar and cider vinegar, amongst others.
Likewise, we can say I have drunk all the finest coffees of the world, but not *I love coffees.