What Is That Fruit That Causes The Hallucinations/Paraly sis?

The Director said, in the comment track, that it was not a real fruit.

On the other hand, I saw and eat a real fruit that looks exactly as the one they eat in the jungle (not in the near final scene)
http://en.wikipedia.org/wiki/Cherimoya and http://www.strangewonderfulthings.com/tips116-seeds.htm

but it does not have any hallucinogenic effect.

It is very delicious (with a hint of Maple Syrup flavor) and has very big seeds.

"Colombian Devil's Breath"(scopolamine) is probably the closest thing in reality. it can be found in the fruit of the Borrachero tree also called Brugmansia in south america. It doesnt make people hallucinate in the traditional sense(as shown surprisingly well in this film), but it does make you like a zombie in a weird passive trance. It can last hours or days.
Vice made a good documentary on it.
http://www.vice.com/video/colombian-devil-s-breath-1-of-2