Depending on whether your system can handle it, or if you're adventurous enough, street food in Siem Reap is pretty good and extremely cheap. Some people will tell you to try the candy, but actually what I really recommend is the bamboo stick. They fill a column of bamboo with rice, coconut milk, and red beans and place the bottom over a fire to cook. To eat it, just snap the bamboo and peel it open. There will be a thin layer of bamboo wrapped around the cooked rice. The tourist price is US$1 for three, though I’m sure you can haggle it lower.