My 2013 Hyundai Sonata GLS is having a problem with the electrical system??

Parasitic draw. Look on youtube for videos to explain it better.

It was some kind of parasitic drain actually, but was the result of some issue with the brake lights that was relatively unusual, so not shown on YouTube, nor anywhere else I could find.... It ended up being a somewhat expensive fix finally, as I not only had to replace a sensor that was faulty, also had to completely rework the entire braking components in the vehicle to avoid messing up the FAR TOO invasive anti theft system that Hyundai unnecessarily puts in their vehicles. Still, thanks for taking a swing at it for me!!

Brake lights draining bats goes back many many decades. The brake pedal fails to contact the brake light switch (on lower steering column) that turns brake lights off. The switch on older cars could turn a bit so the plunger on the switch will miss the peddle, just straighten your switch up and its all good. Caused from loose switch and/or driver releasing foot too fast so peddle comes back too hard. This knocks a switch out of whack, more common on old cars without power brakes. The brake light switch can also just fail and most likely was your issue but' generally the switch is not very costly with less than an hour labor. That is unless a shop simply don't identify this problem really fast like they should have done then they'll charge you for all the extra time they spent looking for the issue on top of things. Such an easily diagnosed issue because the brake lights are stuck on without the brake peddle being pressed down. First thing good mechanics look at on a battery drainer is its brake lights on/off and that switch is working correctly.