The idiom "everything but the kitchen sink" (and variant "everything including the kitchen sink") doesn't refer to a sink filled with dirty dishes. Rather, the kitchen sink (originally the kitchen stove) is being used as an example of a particularly bulky item. "Everything but the kitchen sink" means, roughly, everything except for what would be too large and/or absurd to include.

https://english.stackexchange.com/questions/96582/what-is-th...