I think the key to pulling off any sort of "sweats" is getting ones that fit you properly. Gone are the days of tight elastic-ankled sweatpants or baggy sweatshirts. If you're going to wear sweats, you'll be making a statement whether you like it or not, because they will either say I'm lazy or they'll say I'll wear sweats if I want to and still look damn good. How to look the latter? Buy something plain and fitted. No bagginess, no logos, no weird linings. Plain goes with everything, and fitted always looks good. Here my black hoodie is paired with a short skirt, dressy black flats, and lots of jewelry. Or you could pair fitted sweatpants with heels, if you dare. Just because you're wearing sweats does not mean you should dress down.
Skirt: Talula, Hoodie: American Apparel, Shoes: Calvin Klein, Bracelets: handmade, Necklace: American Eagle