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 need
 * 3 Yeast
 * 6 Fission Batteries
 * Either 10 Refined Punga Fruit or 20 Wild Punga Fruit

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. You can also drop the items in her kitchen and retrieve them later once you have them all.

A good place to find both the Yeast and the Fission Batteries is Blackhall Manor (if you haven't already taken the items). The Yeast is all around upstairs and down and the Fission Batteries are upstairs. Look everywhere, there are 6. There are also another six Fission Batteries and also 3 yeast below the batteries in the Calvert Mansion panic room if the house has been destroyed. Yeast and Batteries can also be found in the Trapper's Shack. You can get the Refined Punga Fruit from the Ark & Dove Cathedral after you have completed the Walking with Spirits quest. There are at least four Fission Batteries in the Lighthouse.

Haley usually stocks multiple Batteries.

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

Trivia
The title of this quest is probably a reference to a method of determining the safety of moonshine that is now considered ineffective. A small portion would be poured into a spoon and lit on fire; the general idea was that contaminated moonshine burned yellow, whereas "safe" moonshine burned blue. However, methanol, a substance sometimes found in moonshine, also burns blue, making this method generally useless.

&lt;EDIT&gt; As a much simpler explanation, small quantities of high-proof spirits have always been known as cure-alls and folk remedies, especially in and around Appelacia where the production of moonshine and whiskey have been a part of the local culture since the arrival of European settlers in America.