Depends in which idea your talking about. Not to mention you can't get fat from something with no calaries. The one drop and your hydrated idea, would not contribute to this at all. It would actually reduce this by a lot. No people would buy pop because, although it tastes good, it costs money and you can gain weight from non-diet pop.
The only useful thing that comes from your idea would be if it was water instead of soda, or a hydrating drink. We really don't need soda so it would just be another thing feeding the ever growing obesity.