Naval slang for the
kool-aid-like drink served onboard ship. It consists of
citric acid and
artificial flavors and colors, it was mixed with
sugar and water to serve. Bug juice actually had no particular
flavor, despite the markings on the envelope. It was instead known by it's color. (
Red (my favorite),
Orange,
Green,
Yellow.)
Because of it's high acid level the contents of an envelope made an excellent cleaner, and was frequently used in the toilets and
bilges.