After reading about inhaling into one nostril and exhaling via the other a few times I was very sceptical but my fear of the cause for my brain fog was bigger than my sceptism. It worked. I did it about four or five times before I felt better and then several more times just because it was working. I had tears behind my eyes and after two weeks of wondering if I was in the early stages of dementia, 20 minutes later I realized that it was my medication. That post was written in for me in 2014. Thank you so much and thank you also, Earthclinic. You have been my go site for a very long time.
I have various minor ailments which I am working on correcting with acv and other cures, but for an immediate remedy for congestion and brain fog, first try breathing in through one nostril and out through the other, then switch and repeat until both nostrils are unclogged. If this method doesn't work, simply walk in a straight line for a few minutes, or try any other type of balancing exercises. These exercises will balance the brain hemispheres, clear up congestion and temporarily rid me of brain fog. I have never found anything to be as effective, not even acv. The downside is that it won't last forever (so take advantage and get some work done that requires a clear head).
Also, a tip about acv: if you buy the expensive mother vinegar, save a couple of tablespoons and pour it into a gallon of the cheap store brand. Soon, the cheap stuff will be growing the mother, and you will have a re-usable, active culture very much like a sponge for making bread.