The extension follows on from a three-year water supply and wastewater services contract agreed between the two parties in 2018.
Jo Dow, chief executive of Business Stream, said: “We are committed to working with all of our customers to help them use water efficiently, delivering financial and environmental benefits – and it’s fantastic to know that the work we’re doing with Greggs is making a positive difference.”
Business Stream is headquartered in Edinburgh, has offices in Worthing and Bradford and employs about 350 people across the group.
The Scottish non-domestic water market opened up to competition in 2008, while the English retail water market opened in 2017.
Ally Stephenson, head of purchasing for Greggs, added: “We’re very happy to extend the current deal and look forward to continuing our partnership with Business Stream.”