These accumulate all sorts of dust and crud and I occasionally carry 'on the go' sweets in them
which once or twice have melted.
I was hoping to find some disposable containers (coffee cups etc) that might make a neat liner, but the holders on my mk4 jazz ex are unusual shapes.
I have probably been a a bit slow here, but I have only just discovered the cubby holes have a rubber liner at the bottom, with a small tab so they can be removed for cleaning.
At least they have on the mk4 ex trim level.