This is most likely not the best forum to ask about the science of creatine and brain function (although there is at least one medic on the forum).

If you could tell us more about what it is that you call "brainfog", perhaps you could get some tips from the meditation POV. Is it some form of dullness or tiredness perhaps? Does it happen on the cushion or off the cushion? How does it manifest itself? If it happens during meditation, how are you adjusting your practice to deal with it? Are your diet and sleep habits in check?