Example of a food stored on a Type IXC boat (12 weeks)
494 lbs. fresh and cooked meats
238 lbs. sausages
4,808 lbs. preserved/tinned meats
334 lbs. preserved fish
3,858 lbs. potatoes
397 lbs. dried potatoes
3,428 lbs. other vegetables
1,226 lbs. bread dough
2,058 lbs. preserved breads
463 lbs. rice and noodles
595 lbs. fresh eggs
917 lbs. fresh lemons
2,365 lbs. other fruits
551 lbs. butter and margarine
611 lbs. soup ingredients
408 lbs. marmalade and honey
309 lbs. fresh and preserved cheese
1,728 lbs. milk
441 lbs. fruits juices
154 lbs. coffee
205 lbs. other drinks
441 lbs. sugar
132 lbs. salt
108 lbs. chocolates
Breakfast would usually consist of coffee, buttermilk soup, biscuits, hardbread with butter or honey and eggs. Lunch would be soup, potatoes, cooked meat and vegetables, and fruit. Dinner included sausages or canned fish, cheese, bread, and coffee, tea or chocolate.
More details can be found here:
http://www.uboat.net/men/foodstuffs.htm