If you arent the original owner of this car then I betcha the owner before you put vinegar in the coolant. Some people do that when they flush their own rads...its supposed to help clean out corrosion...never done it myself, but its not uncommon. Vinegar eats rust, so people believe it will do a rusty system some good.
But, if youre smelling it, you will want to have that checked. If you smell coolant, even if its overpowered by vinegar, thats not good. It can be pretty serious...at worst, a blown head gasket...so get it looked at.