Soda
From KeenWiki
A can of pepsi in the 1980s style next to the keen SODA which is probably based on the pepsi.
Soda cans found on Mars look surprisingly like cans of Pepsi — they use the Pepsi colors, and the side of the can has the letter 'P' visible on it as well as part of the logo. It may well be Pepsi; having taken toys from Earth, the Martians have likely taken Earth soft drinks with them as well.
As there have been issues with the use of Coke and Pepsi in advertisements and songs, it is possible this affected the name of the item, changing it from "Pepsi" to the neutral "Soda".
Similar soda cans can be found in Keen 2 (Vorta-Cola) and in Keen 3 (Diet Vorta-Cola). Bottled sodas can be found in other games: Shikadi Soda (Keen 4) and Bloog Soda (Keen 6).
