King coconut is a type of coconut fruit cultivated in Sri Lanka where it is known as Thambili. It is sweeter than regular coconuts. King coconut is short in stature and commonly found in Sri Lanka, and the nuts of which Sri Lankans regard as a "living pharmacy" is the most versatile and medically practical form of the coconut plant available. Sri Lankans sell and consume thousands of them on a daily basis.

Compared to the aerated waters that are usually artificially coloured and flavoured, the natural coconut drink refreshes and purifies the body. In many Sri Lankan ayurvedic remedies the king coconut has been prescribed to cure many ailments related to impurities in the system.

The king coconut is a well-known source of carbohydrates, vitamin E, iron, calcium and phosphorus. It also has a high dietary soluble fibre and appreciable amounts of protein and fat.

King coconut water has been used from time immemorial as an ayurvedic cure. One of the most common cures is a mixture of "aralu" powder (Terminalia chebula) added to the water of one king coconut. This concoction acts as a very effective laxative.

This "aralu brew" according to Sri Lankan ayurvedic practitioners has the necessary properties to "expel heat from the body" therefore resulting in a feeling of freshness. This feeling of freshness is due to the brew’s ability to balance the body’s electrolytes.

The water of the king coconut is naturally sterile and therefore it is a good substitute for saline. In World War 2 both American and Japanese military doctors injected king coconut water into patients veins instead of sterile glucose solutions.

Countries like India, Malaysia, Indonesia, Fiji and the Philippines have started to popularize the use of this all-purpose-wonder "drug" and have now started to process and preserve it for export.

Coconut water has a nutritive energy value of 17.4 calories per 100 gm and 0.1 g protein, 0.1 g fat, 4 g carbohydrates, 0.02 mg calcium, 0.01 mg phosphorus and 0.5 mg iron.

Dr. D. P. Atukorale, the well known cardiologist, has stated that tender coconut water has the medical capability of being used to feed infants suffering from intestinal disturbances, oral rehydration, to keep the body cool, to apply on the body to prevent prickly heat and summer boils and also treat the rashes caused by small pox, chicken pox and measles. He says it’s a good tonic for the old and the sick.

It also increases the flow of urine and can be used as a blood plasma substitute because it is sterile, pyrogen free and does not destroy blood cells. It also contains organic compounds that have growth promoting properties. According to Dr. Atukorale ayurvedic concepts believe that "it is unctuous, sweet, increasing semen, promoting digestion and clearing the urinary path".