Hello everyone. A 2006 battery/electrical question?

Hi yall. A friend of mine has a 2006. And the guy thinks his battery is dead. His brother thinks its the starter. It was not 2 whole yrs ago I had to do a google image search about how the battery's hooked up (red+, blk-), and put it in front of him cuz he'd convinced himself it was the opposite and already blew the big fuse. This was the brother w/ the starter diagnosis. But anyways, for lack of jumper cables or a trickle charger, I remember putting a good battery in where the dead one was, starting it up n let it have like 5-7 min to run, n then taking it out, put dead battery back in, n good battery back in where it came from. And then driving it around for like a half hour to charge it up. So my question is, can you do that to a 2006? Or does it have too many delicates in it or will it even keep running if you disconnect the battery while its running? Or will somebody get fried? Thanks in advance! I'm so glad I just came here first.