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.

To start this quest, find Sierra Petrovita at Girdershade. Girdershade is located west of Jocko's Pop and Gas Stop or SW of Smith Casey's Garage [You will go to the garage during a Main Quest].

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".

Exiting her house, you are confronted by her neighbor, Ronald. He will pay you the same price for those Quantums, double if you are good enough to persuade him. He thinks giving her the bottles will let him do the "horizontal bump" with her. If your speech skill is high enough, he will pay double. You also have the option if you have the Black Widow perk to do a threesome in exchange for him finding the bottles.