Subject: Why do straws float upwards from a glass of soda?

I often drink lime soda in India, where I am now studying.  The straws always 
float upwards and eventually fall out of the glass, until I drink about a third 
of the soda.  After that, the straw stops floating upwards and remains in the 
glass.  Why does it do that?

Re: Why do straws float upwards from a glass of soda?