While I don't intentionally do long-term fasting (I may skip a meal, or as the trendy crowd calls it, intermittent fasting), I would imagine if I did, I'd break fast with something that wouldn't boost insulin levels much. So that would mean nothing carby or sugary. I'd use food that was protein with a good fat component (fat providing you with an energy boost). So I guess my go-to would be either some eggs cooked in butter, or a nice piece of cheese - if you eat dairy.

I have been doing intermittent fasting for 5 days. I eat my first meal around noon and then my second around 4. I haven't been feeling sick from it and I eat like a pig for my first meal, I am usually pretty hungry by the time its done cooking. Sometimes I feel kinda heavy after eating so much, especially since I eat a ton of bacon but besides that I haven't had any issues. I usually eat 8-10 pieces of bacon, 3-4 eggs, 1/4 avocado and some steamed broccoli.