Darran, how about linking up with Gardiners for that big contract of yours? These big firms like to show how "green" they are and if they have a window cleaning contractor who's serious about reducing water weight and transport costs they can boast to all their clients.
Is it a supermarket chain, by the way? If Gardiners make a drinkable (potable) version then reducing weight in all those mineral water bottles they sell would reduce their transport costs by a third by this time next year.
In fact if it was Morrison's then they could ditch their lorries and call themselves Van Morrison. What do you think? Perhaps they could launch a new drink and call it Green Rhino ...
Do they have chemists in-house like they do at ASDA? They could offer it's prostate protection properties in a Cranberry Juice mix.
Tosh would buy it. He's pretty green.