I wouldn't try the gatorade. It has alot of sugar in it and sugar will upset the bacteria in his intestines.

It could be pasteurella...

Two types of bacteria, Bordetella and Pasteurella, are the common causes of respiratory infections in guinea pigs. Clinical signs include sneezing, nasal and ocular discharge, decreased appetite and lethargy. In some cases, a guinea pig will become seriously congested, making breathing difficult.
http://www.petschoice.com/petinfo/guinea_pig.htm



Information about pasteurella. The page is about the disease in rabbits, but it's the same thing.