What kind of fuse would I need fir my power outlet

It is possible that the issue with the rear power outlet not working on your 2016 Hyundai Sonata is due to a problem with the power outlet relay in the engine fuse box compartment. You should inspect the relay and see if it has any visible damage or if it is loose. If it is damaged or loose, you should replace it. If the relay looks fine, you can check for any other fuses in the engine fuse box that may control the rear power outlet. If you are not familiar with electrical systems, it is recommended that you take your vehicle to a qualified technician for further diagnosis and repair.

This fuse box diagram show a power outlet fuse in the inside fuse box. It also shows two fuses and a relay in the engine compartment fuse box.
https://www.autogenius.info/hyundai-sonata-hybrid-2017-fuse-box-diagram/
The relay says for 3 power outlets
One of the fuses says for cigarette lighter
If all the fuses are good the outlet which does not work may have shorted and blew the fuse. Check outlet to see if it has power to it.

Year/make/model?? To have two defective power outlets would be uncommon. Suspect a power supply issue ( most common ) to outlets. You may have missed the fuse that supplies these outlets. Supply me with make/model and I will give exact location of fuse that needs to be checked

Well... because there can be several things that cause this issue, you want to start with the process of elimitation. Is your car powered on when you try and use the outlet? Most veichels will not allow power to the outlets when powered off.
Observe the outlet and remove any foreign objects from the outlet, there may be a fuse or metal from a broken acessory stuck in the outlet.
Start by pluging something that works into the outlet (like a cell phone charger wit an led to indicate power) locate your veichels fuse box as per instruction of the cars manual. Remove fuse cover and locate the fuse location of the outlet in question, often labeled power or accessory. Observe the ratings of the fuse and be prepared to replace it if need be (it's good to keep common spare fuse for your veichel in your glove,trunk,ect). Remove the fuse and use a fuse tester to test the fuse or look to observe if the fuse is blown, if so replace the fuse, if the led on the charger plugged into the outlet emit's light then you have solved your problem, and if not stop work and call a mechanic or post another question. There are other things you could do but nothing that I would advise without you asking.
good luck and thanks
Questions? Just ask! Mr.Mike

Check the fuse in the instrument panel junction box, left side of dash panel. Tan color box, power outlet 1 or 2 15amp fuse.

The power outlets get their power from the power outlet relay. The power outlet relay gets its power from fuse #21 in the Power Distribution Center (PDC) in the engine compartment. It is a 20 Amp fuse. If the other power outlet works, it is not caused by the relay or the fuse. You most likely would have a broken wire or defective power outlet in this case.

Take a 12v test light and wrap the probe with electrical tape, leave about
1/4" exposed. With the key on, ground the test light wire and insert the
probe into the outlet and touch it to the center power contact. If the light
stays out and you have a good ground, you don't have +power at the
outlet. If the fuse is good, you may have a bad wire or socket. But if it
lights up, we go to the next step. Touch the probe to a known +power
source and ground the wire to the metal side in the outlet. If you don't
get light, check the ground for the outlet socket. Repair as needed.
If it lights up, then you know you have power and ground. Check the
plug on the device you're trying to use. I hope I was of some help.
Good luck.

todytwo

Make sure that the plug is of the right kind. If the fuse looks fine, test the power outlet with some tester to make sure that there's/n't power.

The worst scenario is that the wire has come loose.

if the fuse is good, then remove the outlet and check for power and ground at the outlet. If they are both there, then you need to replace the outlet. Also sometimes the outlet won't get grounded off of the casing so it won't work, which you also need to replace the outlet. nine out of ten times you replace the outlet.

some power outlets need the key on to operate..use a known good devise to test again with different key positions ...otherwise check fuses for ACC. and replace as needed and test again