Cards are used along with Energy Drinks to upgrade a Manager or Business.
The cost increases with each upgrade, so you will need more cards and energy drinks each time.


In the example above, Robbing Hood is level 1. The 1/5 indicates that you have only 1 Robbing Hood Card and need another 4 to upgrade him and to pay another 250 energy drinks. When upgraded to level 2, his bonus is to increase the speed in all Businesses by 2!