how can I save them /
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Try soaking them in water for a few hours -- after a day or so, rinse them and try one to see whether the vinegar flavor has softened a bit. Let us know what you try!
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You could also try straining the sauce and adding sugar to it (to taste), bring to a boil and put the cherries back in.
I would rinse them very well and soak them for a few hours to overnight in sugar water before serving. Anything you do to the brine will probably make them unsafe to be stored for a long period of time however.
Then find a new recipe for your next batch. I like these Spicy Pickled Cherries: http://www.putsup.com/2009/06/cherry-bombs-pickled-cherries-are-weird.html