Your blood sugar is probably dropping causing you to have wild swings in hunger.
In this case, injesting juice or coffee like the other posters suggested will only exacerbate the problem, not help it. I don’t understand all this new age “Juice Fast.” stuff. A fast is a fast. You don’t eat anything with caloric intake, juice included. I can’t even figure out the juice thing - take away all the good stuff, the fiber, and drink the nectar of the fruit, which is basically empty calories.
You may as well have a Pepsi Cola fast if you are going to juice fast, LOL.
Sit tight for a day and it usually passes.
I am a fan of the Atkins Diet for normalizing your sugar throughout the day. I was considered a Syndrome X, not really a diabetic, but maybe pre-diabetic before adopting an Atkins’ Nutritional Approach to my life.
Perhaps if you adopt this approach (and the Atkins Diet is nothing more than a primitive caveman diet), you will probably have an easier time fasting altogether on days you abstain from food. Your appetite becomes more managable.
I also beleive fasting should accompany some rest and reflection and prayer, that you shouldn’t be working while you are doing it.
If you have some medical condition I am unaware of, please consult with your physician first.