hello, I have experience with smalls fastings over all, thouth I also did a six days fasting once. It's very interesting how the body adapt to fasting in short times and feel full energy and in a long term (more than three days) feel so calm, in peace, but what I surprised was that my mind worked perfectly, in heavy ketosis. I think the best manner to break fasting is eating a medium heavy meal with a lot of protein but "digestion-friendly", low-average fat, zero carbs meal.

Excuse me if I make mistakes because English isn't my fist language.