Buy OSRS Greenman's ale
Greenman's ale is a members-only drink in Old School RuneScape. When you drink it, it restores 1 Hitpoint and boosts your Herblore level by 1. It also lowers your Attack, Strength, and Defence by 3, so plan around that. The Herblore boost can help you mix a potion that is just above your level.
You need one Greenman's ale for the quest Recipe for Disaster/Another Cook's Quest. The Lumbridge Cook says it is the official sponsored drink of Castle Wars.
Players can brew this ale with level 29 Cooking. Brewing uses 2 buckets of water, 2 barley malt, 4 harralander, and a pot of ale yeast in a fermenting vat. A batch gives 281 Cooking experience and takes about 1 to 1.5 days to ferment. Buying the ale skips the wait and the ingredient cost.
There is also a stronger version called Greenman's ale (m). It is the mature form of this drink, and a batch has a small chance to mature on its own.
The ale weighs 0.55 kg. It is tradeable and noteable. It cannot be stacked or equipped.