5 quarts a day wouldn't be too far off as they were supposed to get 10 lbs green or 8 lb roasted beans per day. The Union army ran on coffee! There was no blockade to keep it from being imported, either, and it was often a trade item with the rebels. They had tobacco and the Yankees had coffee! More than a few truces were arranged for a mutually happy exchange.
For many generations, Americans drank awful coffee. Didn't have no fetchin' up! That's why we developed the habit of milk and sugar in the drink. Later, beatnik coffee houses and later still Starbucks and others like them imported much better beans and American taste in coffee was upgraded.
The Civil War soldier often ground or mashed his beans and mixed the result with his sugar ration, so a boiled pot of coffee had the sugar right with it. The beans were issued because it was pretty hard for conniving merchants to pad the ground coffee with dirt or other substances - coffee was something the government rarely was cheated on. Quite a few years before the government had stopped liquor rations, including beer, to the army and coffee was substituted.
Several soldiers wrote that they were always very grateful for a nice wash if they had the water, a pipe and a cuppa joe!