Lime is a Mountain Dew flavor first released as a flavor shot in a test market release of a touchscreen soda fountain machine called Pepsi Fusion (designed to compete with Coca-Cola's Freestyle machine) for a short period in 2010.
(2010) Pepsi Fusion test market release
In 2009, Coca-Cola released a touchscreen soda fountain called the Coca-Cola Freestyle. A year after, PepsiCo quickly responded with an equivalent touchscreen soda fountain called the Pepsi Fusion, designed to compete with Coca-Cola's Freestyle machine.
PepsiCo then conducted a test market release in 2010 in various restaurants for a short period of time. The flavors available in the Pepsi Fusion machine were Lemon, Lime, Grape, Orange, Cherry, Strawberry, Raspberry, and Wild Berry, eight flavor shots.