Sodexo already have apparently:
Sodexo says no to plastic straws and stirrers
24 May 2018
Sodexo in the UK and Ireland has banned the purchase of all plastic straws and stirrers, and committed to phase out single use plastic bags and polystyrene foam items such as cups, lids and food...
They have the re-usable cups at Twickenham too for the rugby, they add £1 to the first drink bought, and then as long as you bring the cup back when buying the next, they charge 'normal' price for the next drink.
Alternatively bring them all back at the end of the game and get what you are...