It is really a funk you're smelling an not an ammonia smell, right?

If you smell ammonia when you sweat a lot or afterwards when you shower, that means you probably should be taking in more carbs (or you have a high protein, low carb diet), because you're using more amino acids for fuel than carbohydrates. That could be dietary proteins primarily, but if your metabolism has changed at all or if you're doing high intensity workouts, you may just be burning through your carb stores more quickly than you're used to. it could also indicate muscle cannibalism, though I believe your body would turn to dietary protein sources first.

Just something to throw out there--but unless you're on Adkins or something, it's unlikely you'd smell like that from moderate to light workouts.