http://www.allaboutfasting.com/fruit-fast.html
Apple Fast - I have done this and it is not a bad short term thing to try.
You actually begin the day before, by eating a light dinner, a salad or vegetables or rice. Don't "stock up" on food out of fear of being without the next day or you'll just be making it harder on yourself. And, if you're a coffee or caffeinated beverage drinker, cut those back as far as you can; you won't be drinking them during your fast.
Plan on 3-4 apples per day, organically grown if possible, and ripe, not green. Take time for your "meals": sit down, enjoy the apple, savor the taste, be quiet and notice your bodily reactions, chew slowly and well.
Drink at least 2 quarts of water throughout the day. It should be room temperature or warmer. You can add fresh lemon to the water if you like; it will help with cleansing and give you a little flavor. If you feel chilled or crave something warm (maybe because you're missing your coffee), gently warm the water.
Take it easy for the day, be kind to yourself. Take naps when and if you feel like it. Light exercise like stretching, walking or yoga are good. It's a good time to read something inspirational, but stay away from reading that takes you away from yourself, or wraps you in complex plots, or is at all stress provoking.
There's no need for enemas, you can leave the bowels alone. If you want, you can add a psyllium husk cleanse to your routine by adding 1-2 tablespoons of natural psyllium (available in most pharmacies, even Wal-Mart, in the laxative section) to one of your glasses of water. Do this once per day. This will aid in your bowel movements and will absorb and help eliminate any stagnant material in the bowels. Or you can wait til after you've broken your fast to take the psyllium.
The day you break your fast, ease into food a bit slowly. Perhaps some other fruit besides apples for breakfast and salad or soaked brown rice and vegetables for lunch, and then normal eating after that if it was a one day fruit fast.
For a three day fast, continue eating lightly throughout that fourth day, only resuming normal foods around midday to evening of the fifth day. Once you've returned to normal foods, continue to be aware of what you're choosing to eat and why.