The promotional deals, which Cocktail aim to seal by winter, will push the gourmet nature of GBK's menu. GBK does not want to promote its burgers as fast food but as nutritious, sophisticated and made with the best available ingredients.
David Sykes, managing director of GBK, said the company had faced difficulties in reaching certain key demographics, and is "very excited about the potential of partnership marketing".
Sykes hopes the appointment will "maximise our marketing and target specific audiences effectively, while raising knowledge of our gourmet credentials".
Cocktail has previously paired LoveFilm and Monkey Magazine; the online DVD rental company offered readers of the men's weekly one free DVD from a choice of six classic titles. It has also linked Random House with Monsoon, Magic 105.4 with The Evening Standard, and Maxim with Burton.