[Svonne]

U-70's Interrogation Report has some info on food.

http://www.uboatarchive.net/U-70INT.htm

VII. FOOD CONDITIONS ON BOARD U-BOATS


Food conditions on board U-Boats seem on the whole to be exceedingly good. Translation of a document captured from "U 70" showing the menu for 42 days is given in Appendix I. This U-Boat had left Heligoland on 23 February and had been at sea for twelve days when she was sunk 7th March.
Survivors from "U 100," which had also come from Germany, stated that the food supplied to U-boats was of the very best. The commander, who was training for the command of a U-Boat, said that it was better than he had had in the "Scharnhorst" and ashore. Fresh fruit, oranges, lemons and apples were liberally supplied for the crew.
This boat had been at sea for nine days when she was sunk.
On the other hand a medical report on the survivors of "U 99," which had come from Lorient and had been at sea for 24 days when she was sunk, indicated that the food was not so good as in the other two U-Boats.
The medical report was as follows: "I examined today 33 other ranks. I found their state of health to be poor. General nutrition was poor. A large percentage of the men were suffering from and infected with gingivitis and an appreciable number were anemic (five out of 33 markedly so, to a clinical degree). Eight out of 33 had marked oral sepsis.
I conclude that the men have been on a very poor diet, markedly defective, especially in protein, fat and fresh fruit, vegetables and similar sources of vitamin "C."
Signed: R. SCOTT
Captain, R.A.M.C."


Here's a sample 42 day menu here in the appendix of the doc.



Breakfast: Coffee, cocoa or soup, jam or butter or honey and an egg on dam and.
Sunday
23 Feb 1 Liver, cabbage, potatoes, fruit
One kipper, liver sausage, butter, bread, coffee.
24 Feb 2 Black or liver sausage, sour cabbage, mashed potatoes, fruit
Sandwiches, butter, bread, tea.
25 Feb 3 Beef Steak, cauliflower, potatoes, fruit
Herring salad, sausage, butter, bread, tea.
26 Feb 4 Pigs' trotters (Eisbein), sauerkruat, mashed peas, potatoes, fruit
Sausage, Edamer cheese, dripping, bread, tea.
27 Feb 5 Roast beef, French beans, potatoes, fruit
Potato salad, fresh sausage, butter, bread, coffee.
Friday
28 Feb 6 Sausage, cabbage, potatoes, fruit
Fresh sausage, Camembert cheese, butter, bread, coffee.
1 March 7 Rissoles, mixed vegetables, potatoes, fruit
Tongue sausage, Emmentaler cheese, butter bread, tea.



Here is US Navy Cookbook from 1945 too.

http://www.hnsa.org/doc/cookbook1945/index.htm#toc