googling doing serious research I came across the The New York City Library website. The Library has collected more than 40,000 restaurant menus dating from 1851 and have digitized them. They are now available on the library’s website for all to enjoy, including this 1942 menus from the Pennsylvania Railroad –
Note the mention of rationing under beverages, and also the term “Postum.” I had to look it up On Wikipedia –
Postum is a powdered roasted-grain beverage once popular as a coffee substitute. The caffeine-free beverage was created by Postum Cereal Company founder C. W. Post in 1895 and marketed as a healthful alternative to coffee.
The “instant” drink mix version was developed in 1912, replacing the original brewed beverage. Postum is made from roasted wheat bran, wheat and molasses. This 10‑calorie beverage is caffeine-free, fat-free, trans-fat-free, sodium-free, and kosher.
Although the Postum Cereal Company explicitly stated in its advertising that Postum did not taste like coffee and was not a coffee substitute, the drink enjoyed an enormous rise in sales and popularity in the US during World War II when coffee was rationed and people sought a replacement.
There are more wartime menus on the website, but I picked this one as it reminded me of that great 1940 swing song “Pennsylvania 6-5000” recorded by Glen Miller and also the Andrew Sisters (which you can listen to here).