In my experience, your body will "learn" to deal with longer periods without food -- you'll adapt to burning fat for energy. A bonus of this is, you may find you're not having hypoglycemic symptoms anymore! I find when I have to skip a meal or eat way later than I'd planned, that I'm fine -- I may be hungry, but I'm feeling generally good.
The one thing that throws a wrench into attempts to fast, for me, is eating sugar or refined carbs. As long as I completely avoid that type of food, fasting is do-able. (Not to say easy :lol: )
On days that I fast, I try to have just water and tea until dinner time, and then have dinner as usual. The entire day usually ends up to be 600-800 calories.
I have tried black coffee in the morning -- and that resulted in a nasty blood-sugar crash. But I've also tried coffee with coconut milk, and have had mostly good results with that. I do best when I can stick to tea, though.
Right now, I'm aiming for 2 fast days per week, and taking flax-seed oil on my 'eating' days.