Nisa has raised £100,000 in the last four months for The One Foundation.
The charity, which supports clean water projects across the world, has been working with the convenience store franchise since it became part of the Co-op Group in 2018.
The convenience retailer has raised £626,809 for the organisation over the past three years.
According to the symbol group, 3p of every litre of sparkling, flavoured or still Co-op water sold in a Nisa store is donated to the Foundation by its independent partners.
The news comes soon after the convenience chain announced its donation of £500,000 to the initiative in March this year.
The Co-op has been working with The One Foundation for 12 years and has also announced a partnership with Water Unite, with each bottle of water sold in its stores going towards the projects.
The convenience store franchise has so far raised over £10 million for clean water initiatives across the world.
“It is wonderful that by doing something as simple as stocking Co-op water in their stores, our partners can make such a valuable contribution to a brilliant charity,” Nisa wholesale category controller Danielle Slyvester said.
“To reach another milestone donation total within just four months of hitting the half a million mark is just fantastic.”