In the cartoon the ponies are shown bathing quite frequently! I'm certain some things are not shown (as each episode is only 22 minutes, screen time is a bit of a premium). As horses and ponies do sweat, I can see them being able to do this without drying out their skin. I'm also going to guess that because they're intelligent, they've developed social norms about relieving oneself. While there are no toilets shown in the cartoon, there are few toilets shown in almost any cartoon. I think it's one of those things that are just assumed. Assuming that, I think they would at least smell freshly cleaned. --I can see Rarity wearing a perfume. --Fluttershy probably is fine with how she smells after her bath. I think she'd choose whatever shampoo doesn't bother her pets. I think she takes very good care of her animals, cleaning up frequently so nothing stinks. So her cottage would probably smell like a mix of small animals and pretty flowers. I can see that mixing with her scent. --Twilight would smell clean, and probably like books and ink. I don't know if performing magic would leave a smell (like how electricity can leave the smell of ozone). --It depends on what Rainbow Dash is doing. If she's working with the weather I think she'd smell like breezes and rain. If she's been working out on a routine, she'd probably smell a bit sweaty afterwards. --AppleJack works on the orchard and fields. I imagine after a hard day's work she'd smell sweaty, dusty, with a mix of apples. I could swear there are cows and pigs on the farm, as well as fields. Soooo, depending on what she's doing, she may not smell too nice at the end of the day. I think she'd spend her evenings relaxing in the tub. I can see AJ smelling like her shampoo she uses. --Pinkie Pie would probably smell like bakery and sweets. The smells would probably stick to her coat. Considering she lives above the shop, I can see this being reasonable.