I love fasting. I've finally gotten really serious about it and restricting carbs in the past 4 months. All that energy put into food and food preparation is consolidated into shorter periods. Of course I eat low carb / keto.
My A1c has dropped and my variability has dropped. My A1c result from last week was 4.6, which is my lowest a1c since I started measuring a1c (and I have been diabetic and measuring for 9 years now).
The biggest tool that has allowed me to do this safely is my freestyle libre, which lets me see trends and patterns. I found out I need to take 2 units of fast acting as soon as I wake up in order to keep my line flat... I found out just how much variation in insulin requirements happens across the month (and can react).
I typically fast 16 - 20 hours a day. I eat when I'm hungry. I would like to try a longer fast up to 48 hours, but haven't got to that yet.
When fasting I do still take coffee (with cream in the morning, otherwise black), and broth, and water. If my sugars drop too low, I do correct using small amounts of sugar in the range of 1 - 4 g even while fasting (this has to be done as I'm on insulin and my target is to keep blood sugars in the 70 - 90 range all the time).