The Buddhist Diet
What people eat as Buddhists depend partially on what practices they are following, but these two pages are very useful to find out general restrictions, especially if one is following all the precepts strictly:
How is sexual misconduct related to diet? In the Shurangama Sutra (Mahayana school), The Buddha explains how the "Five Pungent Spices", including garlic and onions, are forbidden:
Beings who seek samadhi should refrain from eating [the] five pungent plants of this world. If these five are eaten cooked, they increase one’s sexual desire; if they are eaten raw, they increase one’s anger. (2)
So if you wondered why they can’t eat garlic, at least if they have taken precepts, now you know. Here is another page that describes the monastic code. Mango was once forbidden because it was too cooling, but it was later repealed and allowed to be eaten.
If you are interested in what the precepts entail, a page that describes them with a good list of footnotes is helpful.