Vinegar cannot wash out a perm. Even though vinegar is acidic, applying it to hair does not break the chemical bond altered by the chemicals in a perm.
Vinegar strips moisture and oil from hair shafts because of its acidity. If left on the hair long enough, vinegar can also cause the hair shaft to swell. It may be most beneficial to wait for the perm to grow out as there is no chemical or treatment to remove a perm once applied. To reduce unwanted damage to chemically treated hair, ask a professional before applying any treatment to permed hair.