Extra product in popup cart.

[steffeen]

Hello,

I want in my shop when people add a product to the cart to offer the option to add another product in the cart popup.

 

The product is related to all products and is a "more sale" technique I want to archive, its low cost and just to make people buy it I want in the cart popup an option to make people "Check this box and get a free water with your order" e.g.

 

Anyone know how this is achievable? I have access to the back end codes and know my php and javascript, but I can't see a solution here.

 

Any help is appreciated.