Yes, vinegar can kill sperm.
The acidic nature of vinegar is thought to be what makes it effective at killing sperm. While there is no concrete evidence that this is true, it is a widely accepted home remedy for contraception.
To use vinegar as a method of contraception, soak a tampon in vinegar and insert it into. This will create a barrier that will prevent sperm from reaching the egg. It is important to remove the tampon after enjoying and to not leave it in for more than 24 hours as this can cause irritation.
It is also possible to use vinegar douches or suppositories as a way to kill sperm. However, these methods are less effective and can cause discomfort.