Nectar is a drink consumed by the gods. In Greek mythology, it is sometimes said to grant immortality to whoever drinks it, although in the myth of the Trojan horse, they were given Ambrosia and Nectar from the goddess Athena, but it did not grant them immortality. It does not grant immortality in the Percy Jackson and the Olympians series either. It is closely related to Ambrosia (both substances possess healing properties). Nectar can be consumed in small amounts by wounded demigods. If consumed by mortals it will kill them.
Percy Jackson and the Olympians[]
Nectar is used as a healing drink when someone is injured. Demigods can drink it, but if they have too much of it, they are in danger of being incinerated. Humans can't drink it at all without being incinerated. It has been implied that nectar tastes like anything the drinker likes (their favorite food or drink). This is shown in The Lightning Thief, when after recovering from the battle with the Minotaur, Percy Jackson is surprised to find that the nectar tastes like his mother's blue chocolate chip cookies.
The Chalice of the Gods[]
Iris tells Percy, Annabeth, and Grover on how concentrated nectar would burn any demigod or mortal to cinders if consumed. It is later added that just a whiff of the substance would put a demigod in a coma.