Cleaning Soldering Iron's Tip - Which Of These Do You Recommend?

[Boris_yo]

As I am beginner in soldering, I don't have any special cleaning equipment and clean soldering iron's tip with damp cloth. So far I am aware of 3 better solutions for this which you can see on attached picture. I initially thought of using thermal sponges but somebody said that they put iron under thermal shock and suggested using soldering removing ball. So I am contemplating between two and if second would be a better choice indeed, I think buying third which is soldering removing ball inside container would be better.

Is using damp cloth or damp thermal sponge bad for soldering iron and why? What would you recommend?