One Londoner has donated 4,000 bottles of water to help keep London's most vulnerable hydrated during the most recent hot spell, but advocates say that number can only last for so long. Jen Martin, who works in program support for My Sister's Place, said staying hydrated is a challenge for the 200 daily participants who rely on the centre for snacks and community. Reusable bottles are not always a practical solution, as having a place to wash and fill them can be difficult.