Sweetened soup? Of course! Honey is a common ingredient in lightly sweet bisques, all sorts of carrot, fruit, sweet potato and squash soups, and in soups flavored with curry, ginger or chipotle seasoning.
It doesn't have to make it sweet, of course (although you'll certainly find dessert soups out there). It can simply make it more complex and balanced. In parsnip or cauliflower soups, honey adds a touch of sweetness that softens the potential bitterness of the main ingredient, and spicy soups benefit from the added, touch-of-sweet dimension that you'd probably only notice if it weren't there. Try drizzling a bit of honey on your favorite spicy soup (or chili!) recipe just before serving for a whole new take on a winter classic.
A sweet bonus to honey is the thickness. Because honey is so viscous, it can help create a thicker soup for recipes served at lukewarm or room temperature.