You get a glass 1 liter bottle in your cabin as a welcome aboard and some cabin stewards will replace it during the week, but I don't think they are supposed to. Only ship I ever had small water bottles left for us was Quantum in Alaska. There was a full case of 500ml bottles loaded in the cabinet below the Lavazza coffee machine. Not sure if that was a holdover from sailing in Singapore or what, but was nice to have.