Lime soda

Lime Soda was a canned, citrus-flavored, carbonated soft drink used by the Militaires Sans Frontieres.

History
It contained moderate amounts of citric acid and sugar to reduce the effects of fatigue.

During the Peace Walker Incident in 1974, Big Boss and his Mercenary group, the Militaires Sans Frontieres procured a recipe for a canned soft drink as well as a recipe for Tortilla Chips either due to neutralizing a LAVtype-G unit or by being supplied with it by Amanda Valenciano Libre while taking her to Mother Base. Brewing the recipe evidentally resulted in the creation of Lime Soda. According to the can, it had four times lime flavor.

Behind the scenes
In the Japanese version of Metal Gear Solid: Peace Walker, it was actually a can of Mountain Dew, which, although it technically existed in the time period of the game, it was primarily added in for product placement as a joke by Hideo Kojima. Also, by entering a code on Peace Walker's PSN that is included in specially labelled Mountain Dew cans, a Mountain Dew T-shirt can be unlocked as well as some recruits with the shirt. There was also a briefing file where Snake and Kaz talked about Mountain Dew, but it was removed from the various Peace Walker releases outside Japan, presumably for copyright issues.

Gameplay
The Lime Soda restores PSYCHE and a small amount of LIFE, and is automatically used if LIFE reaches zero if it is equipped in the item box.

In-game description
"Canned carbonated drink containing moderate amounts of citric acid and sugar for reducing the effects of fatigue. The refreshing citric taste and the mild stimulation of carbonic acid has an invigorating effect not only physically, but mentally as well."

- Lime Soda description from the English version of Metal Gear Solid: Peace Walker