It’s somewhat unclear whether Ent-Draughts are some form of enchanted juice or some form of enchanted water. Certainly it is loved by Ents, as Treebeard keeps a supply laid in. But what is most attention-grabbing about this liquid the effect that it has on hobbits.
Even a single draught will cause feelings of extreme well-being and act as a restorative to good health and boundless energy.
In the cases of Merry and Pippin, it even caused them to grow a considerable amount, making them two of the tallest hobbits ever. Presumably, it would have analogous effects on humans, although this has never been tested – and the only species to drink Ent-Draughts are the Ents themselves. The effect it has on them is unclear, although it is implied to be a mild intoxicant.