From my experience if you are active within the period you are fasting, it feels better. Your mind runs better. You have long periods of stable energy. You have your ups and lows but for the most part it feels good.
Intense exercise doesn’t seem to help me. I can do it, but suffer. Cleaning the house, organising something, painting a wall, going for a walk, etc. are great. You’re not expending a ton of energy, you keep it stable.
If you have adequate amounts of electrolytes, it feels good. If not, it feels bad.
I think a lot of my energy rushes come from cortisol, personally. Fasting is a stressor and cortisol is a stress hormone. I’m prone to that; can’t speak for anyone else. Like the cortisol spikes that come with high-intensity exercise it is not entirely healthy but you have to find a balance.