Well it depends upon each monks i suppose, but i have seen monks eat ice cream.
But some ice-cream do contain eggs, it really depends on how strict the monk is. Like i said, they are still human just like us. But the monks probably have a better chance of getting close to Nirvana than us but not necessarily.
Boybluu pointed that some Buddhist can eat meat and are not vegetarian. This is where different Buddhism traditions come in, the two main ones are the Theravada and the Mahayana tradition.
Us viet people usually follow the Mahayana tradition which is full vegetarian.
Theravada tradition is usually followed in the countries of Sri Lanka, Cambodia, Laos,Burma and Thailand.
and Mahayana tradition is usually followed in the countries of Bhutan, China, Korea, Japan, Tibet, Vietnam, Nepal, Taiwan and Mongolia.
Some info from wikipedia:
http://en.wikipedia.org/wiki/Theravadahttp://en.wikipedia.org/wiki/MahayanaThere are some viet people that choose to follow the Theravada tradition.
Like Boybluu said, some Thai Buddhist go around to peoples houses and ask for food. The monks then would have to eat what ever is given to them. Now one of the reason behind this is that by the monks going around asking for from strangers is to train people's caring and loving for one another and also to train peoples compassion.