Bottle is a weapon proficiency available to fighters, rogues and others with appropriate background. It can be specialized in (if a fighter) but all this does is increase the number of attacks per round.
Anyone can pick up a bottle and smash it over an enemy's head, but there is generally a negative (a non-proficient weapon penalty) and it is likely to break, usually shattering (in which case while a small amount of glass will lodge in the opponent, it usually doesn't do much damage, tending to smash away from the opponent. Few bottles will be thin enough to create little pieces that stick in the opponent, most of these bottles are thick and will leave big pieces (which may act as caltrops) on the floor. Proficiency in bottle includes doing a better job at aiming a shatter, doing 1d4 points of damage (unless exceedingly well placed, most shattered bottles only d0 1d2.) It also allows the proficient person to shatter it just right to use it as a knife. There are no related weapon bonuses for bottle, but you can use related weapon bonuses for whacking people with other things likely to shatter.
Here is the core-rules description:
User is proficient in using bottles as club/knife. Can roll successful STR to break for 1d4 additional damage, can roll successful DEX to not break. (A critical will always break.) Once broken, can wield as knife w/out cutting self. Can throw as club (will break.)