Chris Brown will stink to holy hell ... because he's only allowed one shower every two days.
According to our sources, Brown -- who will sit in jail until April 23 -- is in solitary confinement 23 hours a day ... which means he won't have a cellmate to disgust with his vile odor.
We're told Brown is allowed to work out in his cell and can read library books.
Brown was hauled back to jail after getting thrown out of a rehab facility in Malibu. The judge wants him behind bars until the D.C. assault case runs its course in mid-April. And, if he's convicted, Chris could be transferred to prison for violation probation in the Rihanna case.