I assume you are refering to the round 12V cigarette lighter outlets, not the standard house 110V outlets.
Speaking for the Ford chassis and is very likely the same for the Sprinter, the dash mounted round 12V outlets are supplied by Ford. Those 12V outlets work the same as with any normal car. I think one is powered up with the igition switch on. I think the other is always powered up. Both run off the main engine battery.
In my 2007 2350, the 12V outlet in the passeger side overhead compartment is the only 12V outlet in the coach portion of the motor home. Power to it is supplied by the coach batteries. It is there to utilize typical 12V accessories. One example would be a 12V cell phone charger typically used in a car. It's a place to charge such things in hiding.
I setup that cabinet for charging all kinds of electronics, from cell phones to video cameras, to digital cameras, to navigation, to rechargable flashlights, to laptop computers. Most utilize 110V power via that power strip shown. Note the laptop computer stored on the shelf. I need to make a second shelf above that one for better utilization of space.
BTW: On my 2007, that 12V outlet has a red reset button. That button is related to the antenna signal booster. The 12V outlet and antenna booster share the same electrical box in the wall there. You can't see it in the picture. It is to the left of the white duplex 110V outlet shown.