The vinegar wont’ stain will it?
Clear vinegar is just like water... it won’t stain. Don’t use the apple cider one... that is a brown one. The only thing I don’t like about vinegar is that there will be a slight smell. Vinegar smell doesn’t bother me at all... but if you want to completely neutralize it.. go with the baking soda/warm water solution. Baking soda neutralizes and doesn’t have a smell. Perhaps, 30Moves can provide more info?! I have included her in this post.
You have to use white vinegar, not cider vinegar. White vinegar can act as a bleach and remove color, so test it on an inconspicuous area first.
These are all good suggestions. After you are sure all the milk is gone, you could put a few small bowls of vinegar in the car overnight to remove the residual stench. Part of the problem is that the rest of the fabric in the car picks up the odor, not just the site of the spill. If you spray Lysol or Febreeze, spray all of the upholstery, not just the cloth seat.