The Nuka-Cola Challenge

 is a Fallout 3 quest connected with the Nuka-Cola soft drink. It is also an Xbox 360 and PC achievement.

Upon finding Sierra Petrovita, she offers you to take the Nuka-Cola tour, of which she has a large amount of Nuka-Cola collectibles. After saying that you will take the tour, she shows you around her small 1 room home, and talks about various Nuka-Cola facts, and tells you about some of the items in the room. After the tour she gives you an "Ice Cold" Nuka-Cola.

She then asks you to collect Nuka-Cola Quantums and says she will pay you for them (40 caps each). Once you give her enough to fill her Nuka-Cola Vending Machine, she says she'll give you the Schematic for the "Nuka-Grenade"