A brown shower is what you get *after* hitting a home run.
You see, the guys get together and play Soggy Biscuit in the changeroom, and then give you the biscuit to eat and the Brown Shower.
The ladies come in afterwards to rinse you down with the Golden Shower. Or, if it's old ladies, it's the Golden Years Golden Shower™.
P.S: Golden Shower = urine play, i.e. watersports
Brown Shower = loose faeces play, i.e. scatsports
Soggy Biscuit = circle jerk onto a cracker