Are you thinking about a vaginal douche? It's not supposed to be a mix of vinegar and water. Douche does more harm than health benefits.
The vagina produces mucus, which acts as a natural cleansing agent to wash away blood, semen, and vaginal discharge. Washing the outside of the vagina with mild soap and water with regular bathing is sufficient for good hygiene.
A douche isn't effective in either of cleaning, or preventing STD, or preventing pregnancy.