The following is based on a certain research group but it is possible that some men will not feel any effects by consuming the following:
Alcohol: No surprise here, it isn't good as an overall rule.
Tea: Black tea usually contains less caffeine than coffee, but still can cause issues. Actually tea was named top 5 as the most bothersome among men.
Coffee: While coffee is shown to have some benefits, it apparently is not good for men with prostatitis due to its affect on the urinary tract and known to irritate the walls of the bladder.
Spicy Foods: The key ingredient which makes spicy food generally very healthy is capsaicin. However, this has been associated with a disorder called interstitial cystitis (painful bladder condition) and irritable bowel syndrome
Wheat and Gluten: For many gluten and wheat intolerance are known to cause whole body inflammation. Don't need to be a PHD here - prostatitis is an inflammation of the prostate, so we can definitely do without more inflammation.
Cheers.