Many of these star caps have fixed locations scattered all over the Mojave and DLC regions but can occasionally be acquired by drinking a Sunset Sarsaparilla soda and collecting the cap. With so many of these unique caps to collect, it can take most players until near the end of the game’s story before they’ve acquired enough.
One of the most time-consuming quests in Fallout: New Vegas is "The Legend of the Star," which tasks players with finding at least 50 unique Sunset Sarsaparilla Star Bottle Caps in order to unlock a mysterious treasure.