More than 30 million Fresh Milk poly-bottles and cartons will feature details of a free prize draw during the six-week promotion, which is also offering 10 runners-up vouchers for activity days.
The vouchers will allow winners to decide whether they want to be pampered for the day or enjoy pursuits such as surfing and tracking.
Marketed by the Co-operative Milk Trade Association, Dairygate Fresh Milk is available to independents, CTNs, symbol groups, garages and C&Cs.
CMTA chairman Paul Aston said: “This is our biggest promotion of the year. The Mini Cooper is an exciting car and we are anticipating a record number of entries into a draw which should appeal to Dairygate’s customer base.”