Extensive studies have shown that if you have 1 tbsp before a meal, blood sugar peak is significantly less.
They fed people a cup of lettuce, with olive oil, and another group got the same thing plus 5 grams of vinegar, and a third group dot the same except it was pH neutralized "vinegar". Then they gave them something like 75 grams of potato, and the non-neutralized vinegar group topped out on blood sugar about 20 points lower than the other two groups.
As for probiotics I prefer naturally fermented pickles and kraut, but I will definately put apple cider vinegar on baked potatoes. The potato fiber is supposed to be ideal for culturing the probiotics.