How does caffine affect prostate gland?

Caffeine & prostate. For most men, moderate caffeine intake, such as 1-2 cup of coffee, is not a problem. Actually, more hardcore coffee drinking, such as drinking 6 cups of coffee, may have some health protective effects. But if you have prostatitis or enlarged prostate, you probably want to avoid caffeine as it can exert its diuretic effect and irritate the bladder, and make prostate symptoms worse.
Minimal. Some drinks with caffeine cause men to urinate more, but the extra fluid, and or the acids, such as coffee, may be the factor. If you feel it affects you, use decaf liquids and see if you have the same sensitivities.