What did people eat during WW2?

Less meat and fat and sugar.

Some foods were rationed, but for the most part people ate pretty much the same thing they had before the war... meat and sugar, for example, were rationed, so people ate less of those, but in most places they were still available.
One of the items not rationed in England was carrots, thus the English people ate many carrots during the war and still do.

People living in an Axis occupied country, such as Poland or France had to survive on whatever they could find, or grow themselves, since the German forces would often seize whatever they could find to support their war effort.
Although many foods were rationed in many countries during WW2, people continued to eat the same types of foods, but in differing amounts. The situation was different in different countries and locations. Most meats, sugar and some types of fat were very limited and in some places impossible to obtain. People made use of home gardens and other food sources they could manage at home such as backyard chickens or rabbits.
American troops were treated to some genuine culinary treats: SPAM, beannie weenies, ham and lima beans, Ritz Crackers and peanut butter and Ike even included in his D-Day plans provisions for the early introduction of Coca Cola bottleing plants for the European Theatre.