I assumed they were talking about reused glass bottles. Here (so in Belgium) I buy cases of water bottles with a deposit and return them empty.

The bottles are reused, and the water tastes a lot better than at least my tap water (in Antwerp - the tap water comes from a stagnant canal used for merchandise shipping, and last year for example it turned green and smelled of algae for a while after a ship carrying fertilizer capsized).