From Lost Fables Wiki
Bottled sunlight is just what you might expect from its name. Captured using a special method, bottled sunlight is bright, shiny yellow sunlight trapped perfectly in a bottle. It is an excellent light source, and can be deadly when used against certain creatures which abhor sunlight.
In order to gather bottled sunlight, one needs a correctly-cut diamond, a jar, and a screen of mystic hemp. Hung directly in the sunlight, the diamond will filter light down and trap the sunlight within the jar hanging below. It takes an age for these to fill with sunlight, and the actual size of the jar itself is meaningless. It could be the size of a thimble or that of a huge pot, and it will contain the same amount of sunlight, and take the same duration to fill.
While inside its bottle, if it is a clear glass bottle, it emits sunshine like a torch. This can be extremely useful, creating a permanent, lightweight torch which drives away the creatures of the night. When used for alchemy, it strengthens the effect of the mixture being created. Finally, if the container is shattered, it releases a blinding white flash, blinding anyone looking for a single round of combat after it is thrown. This flash can also vaporize lesser Voudr, though it will likely only thoroughly irritate major ones.