I'm pretty sure the radio, lights and accessories all power off after 10 minutes.
If you were determined to run the 12V battery down you could with patience....
Then a jump start would let you boot up the Spark EV.
Then the DC to DC converter immediately comes online and provides the 12V accessories, actually 13.8 to 14.2V when powered on.
Just like a normal car when the alternator is online.
The 12V battery in both cases just floats on the 12V bus of the car. There is no way to increase this bus voltage.
You could jump start another car.
But I would definitely have the car power off. You don't want your Spark EV dealing with the load of the other car's starter motor.
Or power up with jumper cables in place and let your DC to DC converter send current to the other dead battery for a while. Then disconnect the tow cars and let them give starting a try.
Usually the other car has a problem and a jump won't help.
In fact skip the whole idea, unless you have to be the hero and AAA can't come to your location.
Make up a story about how the Spark can be damaged or something.....
Used '14 2LT w/ DCFC. +78 K miles.
Mostly free charging! Only one LONG visit to the shop....
GM needs Modern Troubleshooting tools for Modern EV's.
3 step Trouble Tree, 1st try car died again, 2nd try not covered / cost $800. 3rd try fixed the problem.