The best chip shops offer a choice of vinegar. There is the common brown sort which used to be called malt vinegar but now comes in bottles labelled "non-brewed condiment". And the clearer, slightly green sort which I was told by the man in the chip shop in Canterbury was onion vinegar: the stuff in which pickled onions are stored.
As well as looking different, it has a more interesting flavour, and soaks far better into the chips and batter than the malt variety. Of course, the purist would say that it is wrong to call these vinegars at all because vinegar means sour wine. Hence our being lumbered with "non-brewed condiment". And I have tried shaking wine vinegar on to fish and chips. It just doesn't work. Just as a green salad with oil and malt vinegar is an abomination.