Cut the plums into chunks (maybe half), dedicating stones. Cut apples into very small cubes (chips). Mix them in a baking dish and sprinkle them with sugar, depending on how many cookies are plums and apples. If you are more sour, increase the sugar and reduce a little vinegar. Sprinkled with sugar fruits remain so 1-2 hours. Then pour the vinegar and water, depending on how much juice you have placed. Water does not pass the level of the fruit tray. Mix well and bake in the oven at about 200C degrees. Sweet is ready when the sauce thickens as honey. Optional finished jam can be seasoned with cinnamon or cocoa. Spill in dry and clean jars while hot, tighten the cap and turn the cap down until cool. I do not sterilize them, but if you wish you can do it.