The egg and grapefruit diet doesn't involve you only eating eggs and grapefruits for days on end. While that might cause you to lose weight and fast, it is not a healthy way of doing it and it doesn't include all the nutrients your body needs daily.
There are a few ways you can use apple cider vinegar to help right your vaginal pH. You can cut it with water (I like mine with warm water and honey) and drink it, or eat it as a salad dressing or marinade. In fact, including it in your regular diet can even prevent imbalance.
Adjust pH by adding PH Up or PH Down solution. Your goal is to get your water in the right pH range for your growing medium. If your pH is too low, you need to add PH Up, and if your pH is too high, you need to add PH Down in order to correct the pH. Re-test to make sure pH is in proper range.