Washing kids couches

We have a pink little couch for DD, but it's really grubby what's the best way of washing them? The fabric doesn't come off, do I just take to it with a wet sponge??

I have a pink foam couch for DD (outer material is kind of a brushed suede type fabric) and while the cover is supposed to come off, its virtually impossible to GET off, so I sponge clean it with warm water and detergent, then leave outside to dry off. Worked a treat on black marks from little fingers playing with our potbelly stove!