Let me see ... Here are a few examples from my wardrobe:
I have some pairs of pj pants which don't look like nightwear and which are so nice that I wear them as loungewear and, in spring and summer, even as streetwear with a long topper. When wearing them as loungewear or streetwear I don't wear them with a matching pj jacket, but style them with various tops and toppers. In fact, I only use them as sleepwear when going to places where temperatures are very low.
I usually sleep in long T-shirts or long tank tops, but choose ones that don't look like typical nightwear. I like to use them as tops as well (over jeans, crops or dress pants) at least around the house or when lounging. In addition, I use them as beach cover-ups.
Tank tops, lace camisoles and simple solid (stretch) T-shirts are used as tops in summer, and as underwear in winter.
Pashmina style shawls are used as toppers, but also as scarves.