Unless you have an infection, you only need to use soap and water to wash the vulva. The vagina takes care of itself mostly. It's a pretty sanitary place - secretions take care of bacteria and flotsom and jetsom that get in there. It doesn't need vinegar. All that does is screw up the pH of the vagina, makes you more susceptible to infection, and makes you smell like a damned pickle.
The foreskin does better if you pull it back and clean it, it makes sense that lady bits would be similar. Douche doesn't work, but at least it has prior plausibility.
Only if you have absolutely no idea how the vagina works, which is why the douche has had such a success historically. The foreskin of a penis is analogous to the clitoral hood, not the vagina. Would you douche your vas deferens?
The "prior plausibility" of the douche is based on ignorance and the assumption that women's vaginas are in a constant state of grossness. There is no actual plausibility to the douche, since, like I mentioned earlier, the vagina takes care of itself pretty well.
I find it insane that we even need to talk about douche...
Trivia: In Scandinavian languages, "dush", pronounced almost like douche, means shower.
Is that an "uh" 'u' or an "oo" 'u'? In America speak, we pronounce it "doosh".