There are plenty of flaws with the California criminal justice system; actually, it can be pretty awful. But it's not all bad news. The OC Register reports that earlier this year, an Orange County inmate successfully persuaded a Superior Court judge to accomodate his special religious diet:
Festivus may only come around once a year...but longtime county inmate Malcolm Alarmo King was able to celebrate it three times a day while locked up at the Theo Lacy jail in Orange.
King's quest for a healthier eating option while behind bars ended with a county lawyer forced to research the origin of Festivus and its traditions and a Superior Court judge recognizing the holiday – which lodged its place in pop culture on an episode of "Seinfeld" – as a legitimate religion.
At issue was King's objection to eating salami, which Orange County feeds its inmates. Key quote:
The Sheriff's Department interviewed King about his religious leanings in May. When asked what his religion was, he answered "Healthism."
A couple of quick points here: 1) Salami is horrible. More importantly, 2) this kind of thing actually happens all the time.
The Religious Land Use and Institutionalized Persons Act of 2000 (RLUIPA!) stipulates that authorities can only evaluate the sincerity, rather than the validity, of an inmate's beliefs. As a result, thousands of inmates who aren't really Jewish request and receive kosher meals each year simply by claiming that it's a religious requirement. As Seattle Weekly reported in 2006, "interviews with Washington prisoners who have declared themselves Jewish and are receiving kosher food have yet to yield an actual Jew."
Sometimes, this can reach the level of farce—like the 2008 case of Norman Lee Toler, a Missouri inmate who won the right to receive kosher meals despite having been disciplined by prison authorities for decorating his cell with photos of Hitler.
Still there are limits. In Strope v. Cline, "a Kansas federal district court rejected an inmate's claim that his rights under the free exercise clause and RLUIPA were violated when authorities removed beef, tomatoes and cucumbers from the 'common fare' diet and frequently served peanut butter." Actually, lawsuits over peanut butter are quite common.
I'd also refer you to the the landmark case, Stanko v. Patton, in which a federal court tossed out the complaint from a white supremacist who said his faith (the Church of the Creator), required a balanced diet of fresh fruit and nuts. This was initially reversed (pdf) by an appeals court, but the district court had the last, exquisite word: "Hate is not a religion and jails do not have to provide nuts and fresh fruits to satisfy the whims of haters."
Haters gonna hate.