I was being a little smart a** ish and I know they are not all clear, but I have found you can achieve pretty good results several different ways. Hope some of these examples may help. I love to photograph, so I hope I stumble across a better way tomorrow!
I have the best luck with clear glass pics by placing them on a table or other platform a couple feet away from a window while its still full daylight outside but the sun is not shining through the window. Put a couple pieces of white paper under the bottles,make sure the camera is steady and always use the macro setting. Like this.