Question:

Are bottle caps muktza or may a child take the caps from the table and play with them on Shabbos?

Answer:

A bottle cap is a kli shemilachto lheter, because it is used to cover bottles, which is a permitted use on shabbos, and therefore it may be played with to provide the children with entertainment. Even after the bottle is thrown away, the cap can still be used on a different bottle, and it retains its old status.

Gmar Chasima Tova

Rabbonim of the Beis Hora'a