Fruit shakes are a staple food item on the backpacker trail in southeast Asia, but in Cambodia they're very popular with the locals as well. They're called "tukalok" in Khmer. I particularly liked the White Rose restaurant in Battambang, which listed 45 different types of fruit shakes. Most of these were single fruit, and they're made by pureeing the fruit and some ice with a bit of condensed milk in a blender. This was the only place I found Dragonfruit shakes, and it made me very happy.