Plenty of water. No caffeine or chocolate. Cut down on hot pepper and other strong spices.

Chemopreventive efficacy of silymarin in skin and prostate cancer. http://www.ncbi.nlm.nih.gov/pubmed/17548792

My understanding is Chronic bacterial prostatitis (CBP) represents a bacterial infection of the prostate gland.

There don't seem to be consistently effective herbal remedies for chronic prostatitis, but quercetin (a compound found in red wine, onions and some teas) has shown some positive effect, at least in limited trials.

Silymarin (found in milk thistle) is being studied in prostate cancer, but I don't see anything on PubMed about it being used for prostatitis. Most cases of chronic prostatitis never have a specific cause identified - some are related to chronic bacterial infection, but lots of the time no infection can be found.