From all of my reading about the Civil War, I can say Coffee, to the Northern Troops was the mainstay of life.
Without food, there would of course be some grumbling but without Coffee, the grumbling was much more vocal and wide spread.
For instance in the book "Marching Thru Georgia" by F. Y. Hedley (Adjutant Thirty-Second Illinois Infantry) Copyright 1884, M.A.Donohue and Co. Publisher, many times he describes how the first order of business when the men stopped for more than 5 minutes was to make a little fire and brew some Coffee.