Zero-calorie soda

Zero-calorie Soda, also referred to as Narc Soda, was a kind of soft drink.

History
Zero-calorie sodas were first developed around 1952 with the creation of the No-Cal Soda by Hyman Kirsch and Morris Kirsch as a method of selling soft drinks to diabetics. Eventually it caught on to the Soda industry and became a large part of the industry.

During the Peace Walker Incident in 1974, Big Boss and his Mercenary group, the Militaires Sans Frontieres, procured recipes for canned soft drinks as well as a recipe for Tortilla Chips either after neutralizing a LAVtype-G unit near Bananal Fruta de Oro, or by being supplied with the recipes from Amanda Valenciano Libre while en-route to Mother Base for treatment. As a result of its R&D Team developing it, they apparently developed a no sugar carbonated drink that was ahead of its time.

Behind the scenes
In the Japanese Version for Metal Gear Solid: Peace Walker, It was actually Pepsi NEX, which was added in as product placement by Hideo Kojima as a joke. Strangely, Pepsi NEX was removed despite being a Japan-only drink. Coincidentally, the design of the model viewer of the Zero-calorie Soda that replaced Pepsi NEX was of Narc Soda, the soda drink that Drebin 893 often drank in Metal Gear Solid 4: Guns of the Patriots.

In-game descriptions
"Excess body fat can lower the odds of survival on the battlefield, reducing mobility as well as the stealth benefits of camouflage. To keep body fat in check, military R&D developed an artificial sweetener which in turn led to the introduction of a non-sugar, zero-calorie carbonated drink that is way ahead of its time."

- Zero-calorie Soda description in the English version of Metal Gear Solid: Peace Walker