I googled "Vinegar" pie and it probably isn't half bad - it was pointed out that the vinegar does the same basic thing that lemon juice would to - add some acidity to the basic sugar taste. But it's one of those recipes that was developed for when you were broke and really wanted something sweet and didn't have much to work with (one lady said her great grandmother who emigrated to the prairies and lived in a sod house in Kansas used to make it in the winter when they had used up all the dried fruit). Why would anyone want to do that nowadays when most of us have, at any given time, access to much better ingredients. It's in the same category with Tomato Soup Cake and Ritz Cracker Pie . I've had both and while they are edible, and the Ritz Cracker Pie does kinda sorta taste like apple pie, why would you substitute processed crackers for apples...?