I am on day 10 of a Water Fast and will probably post details later.
On the first three days of my fast I used small amounts of coconut oil when I felt hunger. It roughly equalled a TBS per day. My favorite brand is Artisana.
I'm sure you've heard that the first 3 days are the most challenging as your body transitions to using fat as its primary fuel source. Unfortunately, if you continue using juice it will postpone or prevent that transition.
Sometimes what people feel is low blood Sugar is a salt imbalance. A small amount of salt, say 1/5 tsp in water often helps. Pink Himalayan salt or Sea Salt is best.
I routinely take a powdered potassium magnesium supplement and continue that through a fast.