I've used Apple Cider Vinegar over the years for various things but particularly for colds. It's very alkalizing which, without going into too much of the science, is good for you.
Basically a lot of what we eat and drink days is acid-forming and our bodies need to be slightly more alkaline for optimal function and health. Apple Cider Vinegar helps rebalnce this by making you more alkaline.
Here's a summary of some other great uses for Apple Cider Vinegar: