I had a can of Relentless, how long before I can have a cup of coffee?!
Unless you have a heart condition, you could drink them back to back. Lots of people will drink 3+ cups of coffee in a row without a problem
I actually searched a similar question several days before. when trying to find the solution I found a way to obtain a free sample of Folgers Gormet Selections full range of ground coffee from http://www.hotfreefolgersgourmetcentral.tk. my free Folgers samples is scheduled to ship in 3 days n i'm so happy.
Good luck to ya