Juice fasting is better than water-only fasting if you need to go to work and keep your wits about you during your fast. Juice fasting can keep your energy level higher while you’re fasting, and it can keep your mind sharp.
Here’s how to juice fast: Don’t eat any food, and only drink diluted fruit juice whenever you want — drink a mixture of half juice, half water. And use juice, not a “juice-flavored” sugary drink.
Even if you drink a lot of juice during your fast, it won’t add up to very many calories. You can fast for a longer time juice fasting than you can with water-only fasting, and it will be less uncomfortable. You’ll experience fewer hunger pangs and less thirst.
The main alternative to juice fasting is water-only fasting, which is more extreme but has some advantages. Read more about water-only fasting.
Read more about fasting.
I've read a lot of books on fasting. I didn't think many of them were very good. But I found two I really liked, and I recommend them if you're interested in trying a fast:
Fasting: An Exceptional Human Experience
Principles of Fasting