In the past I've bought many pickled cucumbers and other veg, but a few weeks ago I bought pickled 'sandwich' cucumber slices (similar to this) which were in sweetened vinegar and liked them much better; the key thing about these pickles is that they are in "sweet" vinegar rather than normal pickling vinegar which is quite sour.
I would like to know whether it's possible, and if so how I can do it, to take a jar of pickles I've bought in normal (sour, not sweetened) vinegar and sweeten it? Can I just add sugar to the vinegar they are in, in the jar? Will that have any effect? If it would have an effect, how long would I need to leave the sugar in there before eating them?