There's a short paragraph in Anna Maria Sigmund's book "Women of the Third Reich" (page 144) that has a little description of some contradictory information about Hitler's reason for going vegetarian. Basically, he became a vegan for practicality and not out of piety, and whenever he ate meat, he would sweat profusely at rallies. Apparently beer drinking made him lose weight (I know a few of my friends would envy this!). Tea was part of his diet too.
EDIT: Just mentioning some examples cited from the above source. Apparently, the menu on August 9th, 1937 at the Berghof consisted of barley soup,p ork sausages, saurkraut, mashed potatoes, and salad. Hitler had semolina noodles and eggs. June 7th, 1943 included orange juice, linseed porridge, rice pudding with herbal sauce, crispbread with butter and some weird paste called Nuxo (Soy and sugar based)
Hope that contributes to something.