At one point or another we have all been annoyed by the fact that a spray bottle won't work if you want to spray something at too much of an angle. So I made a simple mod that lets it work in any orientation. I replaced the hard suction tube with a flexible tube and added stainless steel weights at the end. This way the end of the tube will naturally fall to the lowest point of the container where the liquid will pool. Basically it is a clunk tank. This kind of suction tube is used is a lot of mobile fuel tanks such as airplanes and string trimmers.
For step by step instructions check out my Instructables page: http://www.instructables.com/id/How-to-make-a-spray-bottle-that-works-in-any-direc/