Nuka-Cola Clear formula

The Nuka-Cola Clear Formula  is a quest item in Fallout 3.

Background
The formula describes how to make Nuka-Cola Clear, a type of Nuka-Cola that was invented shortly before the Great War but never mass-produced. It was said to not have as much kick as Nuka Cola, but made up for that with its clear appearance.

Locations

 * The formula is located in the R&D section in the safe on the wall of the Nuka-Cola Plant. R&D is research and development, and is located in the first area to the left, after entering the plant. You must get the key for the safe from Milo, Shipping Foreman.
 * After getting the formula, head to the Red Racer Factory, northeast of the Nuka-Cola Plant, where you will be met by Goalie Ledoux and the remaining members of his faction, Sudden-Death Overtime (you'll find the corpse of one of his teammates elsewhere in the Nuka-Cola Plant). He will offer you 250 caps for the formula or 400 caps if you pass the speech check. You may also choose to "face-off", resulting in the group turning hostile, allowing you to keep the formula for yourself for collection value.
 * You can however talk him to pay the 400 caps and afterwards kill him and his crew without loss of karma. Also you can take the formula again - so that you will have two in possession (maybe only one if you are carrying it with you).

Related quests

 * The Nuka-Cola Challenge (optional objective "Just for the taste of it")

Behind the scenes
This is most likely a reference to Crystal Pepsi or Tab Clear.