With a sharp paring knife, cut an X in the stem end of each grape. Divide between 3 pint size canning jars. Combine the vinegar, sugar, salt, peppercorns, cloves and pepper flakes in a small saucepan and bring to a boil. Stir just until the sugar has dissolved and pour over the grapes. Cover and refrigerate at least 1 hour. Serve with the cheese and crackers or bread.