Once that is completed, Festus will tell the Courier the legend of how Sunset Sarsaparilla came to be. When he is done, the game will report that the quest has failed, then the player character will be given the quest A Valuable Lesson. Complete the quest in order to receive the achievement/trophy "The Legend of the Star."
The story Festus tells about the origins of Sunset Sarsaparilla is not consistent with other information given to the player. He tells the Courier that before Sunset Sarsaparilla was invented, the main choices people had for soft drinks were water or Nuka-Cola. Nuka-Cola was founded in the year 2044, but according to the large bottle at the entrance of the Sunset Sarsaparilla Headquarters, Sunset Sarsaparilla was founded in 1918, over 125 years before Nuka-Cola.
A complete list of Sunset Sarsaparilla star bottle cap locations can be found here.
After the quest has been completed, star bottle caps can still be collected, but will be automatically converted into normal bottle caps. Any star bottle caps the player has over 50 will be converted to normal bottle caps once the 50 star bottle caps have been turned over.
Deactivating Festus with the Robotics Expert perk will render this quest unable to be completed.
According to Joshua Sawyer, the quest was inspired by his experiences collecting Tootsie Roll Pop wrappers as a boy due to a false rumor that sending 100 special wrappers bearing illustrations of a boy dressed as a Native American shooting an arrow at a star would yield a special prize. The story that Festus tells upon completion of the quest is based upon a story that was sent out to children who sent in wrappers and it shares many common elements. A terminal shows that the rumor about a prize was not created by the Sunset Sarsaparilla Company, and was only used to continue the increase in profits that was started by the rumors.