Check the drains to be sure they are not blocked. You should see water draining under your Sorento when you are sitting in driveway after running the A/C. You can buy and oder killer spray at any auto supply store to spray into the vents. If you run the fan after turning off the A/C it will help dryout the inside of your vents as this is the major cause of the oders. Remember the A/C also runs in winter in defrost cycle.
Just check the the type of fluid you are using in the windscreen
washers, somebody on another Kia forum had the simular problem
smelted like rotten eggs, it was i think in the uk, and he was using
a brand from Halfords, when they used the washers with the heater
or a/c on they got this smell.