It depends on my motivation and also how cold it is outside (since I go to the gym in my workout clothes for the most part). If I am really pumped up I will wear pants (not sweats but non-nylon track pants or fitted yoga/running pants)... if I am not really in the mood I wear shorts because once I start sweating I get burned out and want to stop if it not a good motivating day.
Since my cardio normally is morning swims 3-4x a week except for 8-10 weeks when the water temp is too cold. Then I usually spend some time on the heavy bag in the boxing room. About 15 mins, done in the clothes I just worked out in.
Usually a tank top and my yoga capri/ or yoga pants im wearing.
I never understood the sweatshirt and sweatpants thing......I sweat a lot on cardio already.
I only understood the sweatshirt wearing while your running at night or early morning..