Fluid sensing systems and methods, including sensors used to sense various fluid levels in vehicles, are disclosed herein. One aspect of the invention is directed toward a method for sensing a fluid that includes passing electromagnetic radiation through a receptacle positioned to hold a fluid. The receptacle can be configured so that electromagnetic radiation that passes through portions of the receptacle containing fluid is focused. The method can further include determining (a) whether fluid is located in a selected portion of the receptacle based on an amount of electromagnetic radiation that impinges on at least one radiation sensor, (b) a characteristic of fluid located in the passageway of the selected portion based on a pattern of the electromagnetic radiation that is created on the at least one radiation sensor, or (c) both (a) and (b).