FOUL SWEET SMELL?
You didn't say the model or year of your car but by the description of the smell and misting/fog it sounds as you may have a leaking heater core. This is a typical sweet smell and some dripping on the carpets being more pronounced in the winter than in the summmer. Hate to shed bad news on your situation, but you asked!
Try having your cooling system pressure checked and see if there is a leakdown while checking inside the car for dripping or even a hissing sound. A good stop leak such as 'Bars' could remedy the leak for awhile but may not permanently. Give it a try.
PS: By the way, please inform the forum of what you find and your remedy to help others in the future. Thanx