Shlishi,
I just noticed your post; I think my previous one answers your question.
When I started going out, I asked a rov what type of shailos I should be aware of. I was expecting to hear about yichud issues, but he told me not to buy an alcoholic beverage (with a bit of a twinkle in his eye; he knew I wasn’t the type anyway). He said nothing about soft drinks. My posts here are really just an educated guess as to his reasoning.