Soda cans will quench the player's thirst completely when consumed. They can be used by entering the gear window ('G' Key), right-clicking its icon and selecting 'drink soda can (###)'. Upon consumption, a snap, hiss and gulping sound will play to represent the player drinking the can. Be wary as other players and zombies can hear this noise from a small distance.
Mountain Dew is the most rare form of soda in DayZ. Although it has absolutely no special attributes, other players may be intrigued by the fact that you wield it. It may sometimes be used as a trading item, due to its rarity, though it would be very hard to find a player that is really truly interested.
Another point of interest is "the Mountain Dew curse." The superstition is that if a player finds a Mountain Dew, but does not drink it immediately, the player is destined to die very soon. The instances of the death are often very random occurrences, such as snipers on extremely low population servers, stuck/destroyed vehicles, being over-run by zombies, or simply unexplainable deaths.
 DayZ Mountain Dew Locations
There is a rare spawn of Mountain Dew in the town of Bor that is more common than anywhere else.