When ordering a diet soda (no sugar soda) in a cafe or restaurant I would like to be sure I am getting a diet soda and not a regular sugar-infested soda. Because a regular soda, is through all the sugar, far more dense than a diet soda, my idea is to use a simple hydrometer. Ideally this hydrometer would be a simple everyday item that sinks in diet soda but floats in regular soda. I already tested this this idea with some simple items such as coins or small toys. However all tested items either sink in both cases or float in both cases. Anybody has a good idea for a suitable item that sinks in diet soda but floats in regular soda ?
UPDATE although it didn't really answer my question, the experiment suggested by matt_black was too simple not to try out. However what happened when I performed the experiment was that both the can of regular coke and zero coke sank. I discovered there are a lot of video's on youtube showing a can of diet coke floating and only the can of regular coke sinking. So I am quite surprised by my own findings.