Glass Bottle

The Glass Bottle is an item that was added in 1.9 Pre-release 2. Glass Bottles are used to brew potions and Splash Potions with various effects. It is possible to pick up water for potions in the 1.9 Pre-Release 3. You can put them in the Brewing Stand; however, potions cannot be created unless they are filled with water. You can put in various things to make different potions, these include potions such as Instant Health, Fire Resistance, Strength, etc.

Usage
Glass bottles are used to hold potions, as well as the water used to make potions.

The bottles themselves may only be used (right-click) on water source blocks or a Cauldron to fill them. If used on a water source, the water will be unaffected. If used on a cauldron, 1/3 of the water in the cauldron will be removed. Bottles of water are used with the Brewing Stand to make potions.

Because of this, using a cauldron, as of Minecraft 1.0.0, is not recommended, as a single bucket of water placed as a water source can provide an infinite number of water bottle fills, but that same bucket of water placed in a cauldron will only provide 3.

A bottle of water or a potion may be emptied by drinking it, returning the empty bottle to you.

History
The Glass Bottle was first added in the Beta 1.9 Pre-Release 2. They were given an additional function for picking up water for potions in the Beta 1.9 Pre-Release 3.

Trivia
As of Minecraft 1.0.0, When you drop the bottle (Q button as default.) the bottle will appear empty, even if you have potion/water inside.