I have had 'foggy brain' a few times. Kinda 'space out' for a few seconds? Like you were in a stupor?
I woke up with a mild headache on day 6, but it went away after water and lemonade.
My guess the foggy moments are due to low glucose to the brain, since we arent eating enough to fuel our bodies for the work we are doing, and during the time between using up the energy calories from the lemonade, and switching over to convert the fat to glucose to use as energy, we get foggy. Just a theory though.