I've just watched this documentary about Buddha boy. The boy hasn't eaten or drank anything for 8 months while meditating. One scientist there said he is in hibernating state. Is this possible??
No, it's not possible.
There's some fraud afoot, and the TV crew was obviously duped.
Some other people who have claimed to be able to survive on "sunlight alone" or "fresh air" have been tested under controlled conditions (by James Randi and others) and have failed the tests. Testing is easy - just lock them in a room (with sunlight, if they say that's what they need, of course) and make sure before you do it that they don't have any concealed food or fluid sources. Then wait until they get thirsty and hungry.
The ethical issues of these kinds of tests are somewhat problematic, however. Some people may really believe they can survive without food or drink, and endanger their own lives if they undergo a real test of their claims.
In the case you mention, the most likely explanation is that the boy had some kind of fluid source concealed on his body.