there was some sort of 'smell' (I lack a better word)
So there was a sensation in your nose that you partly (but not confidently) identified as smell. It might not have been olfactory, though.
I'm no expert, but it seems likely to me that in addition to any impurities in the water that you really can smell, you're also detecting a sudden change in humidity (especially with the hot water) and/or temperature. Strictly speaking you can't "smell" water, but that's by definition of smell. You can nevertheless in the right circumstances detect water via the mucous membranes of your nose. As you inhale, the air passing over the membranes dries them (or doesn't) by a differing amount. Aside from the fact that you might falsely perceive this sensation as a smell, how dry the membranes are does affect your perception of anything you can smell in your environment. So a change in humidity can result in a change to what you smell.
Even the acoustics of the cup could be detectable (nose, ears, close together, attached to the rigid/resonating boney structure of your skull, you're putting your nose at the entrance to an enclosed space), and could be interpreted as "like a smell" if a smell is what you're expecting from your nose. Although I don't think that accounts for a difference between hot and cold.
So this could well be a biology/psychology question as well as a chemistry one ;-)