It has an orange appearance and typically sold by cans with the slogan "Taste the SUN". Given the numerous vending machines scattered about the ship, and the numerous advertisements seen at Tram Stations, it is easy to tell that the beverage is very popular. From the label on the bottle it appears that SUN has been served since 2190. It is presumably a parody of Sunny D, and Coke-Cola. As seen in advertisements across the Ishimura, SUN is sold in bottles, but can only be seen as cans in vending machines designed to dispense the drink.
It appears that Ellie Langford and her crew took several cans of SUN with them as many of them are found from the command saucer of CMS Roanoke.