Discard stems and leaves; rinse fruit. In a 6- to 8-cup wide-mouth clear decorative jar with lid, tightly pack fruit.
Mix vinegar and sugar until clear. Pour into jar, filling to cover fruit. (If you need more liquid, blend each additional 1 cup vinegar with 2 to 3 tablespoons sugar.) If fruit floats above liquid, push a wad of clear plastic wrap (large enough to reach the rim of the jar) on top of it. Close jar airtight.
Let stand until vinegar is aromatic, at least 2 weeks or up to 3 months. Check occasionally to maintain liquid level; if it evaporates enough to expose fruit, the exposed parts discolor dramatically. Persimmon skins stay firm, but interiors get soft.