Trivia: Upgrayedd is portrayed by Scarface of the group Geto Boys. Mike Judge's previous film, Office Space, included Geto Boys songs such as Still, when the office workers smash the printer. According to the DVD commentary - The explanation given by Officer Collins in the Army staff meeting that Upgrayedd is spelled with two D's for a "double dose of this pimpin'" is a direct reference to the documentary American Pimp, in which real-life pimp Rosebudd offers that same explanation for the spelling of his name.
Trivia: None of the shirts or pants have buttons or zippers. This was intended to illustrate humanity's inability to operate something as simple as a zipper or a button.
Trivia: Hang around after the credits: there's an extra scene.
Answer: The science in this movie is far-fetched at best. Assumedly the pods had some sort of battery backup for emergencies. If the battery lasted 500 years, we can just assume it was secret government technology.