The above video is of a cart somewhere in India that sells roller coaster ice cream. It is made by filling a drum with ice and salt and then, as the drum is rotated, covering the outer surface with milk, fruit juices and bits of fresh fruit. Toppings can be added. It is not the most hygienic looking operation, but I imagine the ice cream it produces is a tasty treat.
These types of carts seem to be popular throughout southwest Asia. Many are motorized, but some, like the one in the video, are hand cranked. My hat is off to the guy who spends all day cranking that thing.