Air kelapa

Coconut water is the clear liquid inside young coconuts (fruits of the coconut palm). In early development, it serves as a suspension for the endosperm of the coconut during the nuclear phase of development. As development continues, the endosperm matures into its cellular phase and deposits into the rind of the coconut pulp. The liquid inside young coconuts is sometimes preferred to the liquid of a ripened coconut. Coconut water from young green coconuts is also known specifically as buko juice in Philippine English. Fresh coconuts are typically harvested from the tree while they are green. A hole may be bored into the coconut to provide access to the "meat" (liquid and pulp). In young coconuts, the liquid and air may be under some pressure and may spray slightly when the inner husk is first penetrated. Coconuts that have fallen to the ground are susceptible to rot and damage from insects or other animals.

Source: Wikipedia