A Spoonful of Whiskey

 is a Fallout 3 quest that is added to the game with the Point Lookout add-on.

Walkthrough
Marguerite will try and convince you that she is sick, and she needs these items to get better. With Medicine and Speech she will admit she makes Moonshine and ask you to gather these items for caps as well as a share of the Moonshine.

You will need*
 * 3 Yeast
 * 6 Fission Batteries
 * Either 10 Refined Punga Fruits or 20 Wild Punga Fruits

* It is a wise idea to travel light and find a way to get the fission batteries and punga fruit to Marguerite. The required items will total a massive 70 lbs., or 80 if you're carrying wild punga; if you're also carrying the required 12 pounds of Yeast, that's 82 or even 92 pounds on top of your other equipment.

It is possible to bring the items per batch to Marguerite. This may be a more weight-efficient way of completing this quest.

Reward
You will receive 300 caps and several Moonshine. You can also repair her still for an additional 100 caps (200 with a speech check).

Trivia
The title of this quest is probably a reference to the song "Just a Spoonful of Sugar" from Mary Poppins.