The standard for most fasters is to drink nothing but pure water. If blood sugar dropping too low is a huge concern, I would suggest doing some experimenting, while being monitored, of course.
My suggestion would be to first, prepare for the fast by eliminating caffeine from the diet for a minimum of 4 days beforehand. If it isn't part f your life anyway, good for you. But for many folks, caffeine withdrawal adds anther layer of discomfort and even complication to the difficult first days of a fast.
Second, I'd suggest experimenting with a somewhat doctored brew. Instead of just water, try a "lemonade" made by adding fresh lemon, perhaps some sea or himalayan salt, honey and/or blackstrap molasses to the water. The blackstrap molasses may seem a bit odd, and may take some getting used to, but would be quite good for the health if you can palate it.
Possibly experimenting ahead of time would provide you with both an effective and enjoyable recipe as well as some confidence as to what to expect. And I believe that the ingredients mentioned would tend to aid, rather than inhibit, the natural cleansing effects of the fast.
If you found this still too volatile, I do know that there are doctors advocating "fasting" while drinking fresh juices of fruits, vegetables and greens. There are books available describing their reasoning, research, and methods. While I've chosen to stick with the water route myself, with good success, their ideas make sense as well.
Since our God is mightily motivated by compassion, is a healer, and rewards those who diligently seek Him, I'd be the first to encourage you to try whatever method works along these general lines, all the while reminding the universe that by His stripes you WERE healed. It's a done deal. You have title to total healing including hypoglycemia. So you are perfectly willing to go all the way to the water only version if God will kindly make manifest in your body the healing that His Son purchased 2000 years ago.
I do believe God will honor your heart and obedience as far as is physically possible. Expect an adventure.