Not even in theory. I live in Germany and can get 500ml of average beer for around 0,50€. That's cheaper than soda in a lot of cases (ignoring the cheapest soda). We can also drink in public legally, and it is socially acceptable.
The cheapest beer and the cheapest soda should be compared, since they both save significantly on marketing and brand costs.
In that case, soda is about 25¢ (ja! Apfelschorle) and beer 50¢ (5,0 original export). Both from rewe.de.