The attack was reported at 5:23 p.m. near Eddy and Buchanan streets.
The victim was riding his bike when the thief approached and attacked him without saying anything, hitting him in the head with the bottle, according to police.
When the victim fell to the ground, the suspect got onto the bike and rode away. The victim was taken to San Francisco General Hospital to be treated for a head contusion, police said. His injury was not considered life-threatening.
The suspect, described as a male in his late teens, had not been found as of this morning. Anyone with information about the case is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.