A crew on a rig used a solvent to prepare the doghouse floor for painting. They applied the solvent by filling a one liter drinking water bottle and punching a hole in its cap. The bottle was left in the doghouse when the crew went off tour. A floorman on the relieving crew was thirsty and drank out of the water bottle containing the clear solvent, ingesting a small amount of the cleaning fluid. He was transported to the clinic immediately for medical treatment and following first aid and observation he returned to work.