I think Freons are odorless, but the oil in the A/C system would probably smell … well … oily. Coolant? I think that coolants – Ethylene glycol and Propylene glycol – are also odorless in their natural state, but are mixed with something to give them an odor. Classically, coolant has a sweet smell, but that’s not to say that it couldn’t have a different smell if the manufacturer desires. But, I’d go with the windshield washer fluid as a first guess.
Easy enough to check. There’s a big container full of windshield washer fluid somewhere under the hood. Likewise the coolant. That’s probably best done at the overflow tank and with the engine cold – why ask for trouble?