Soda goes foamy suddenly for many of the same reasons that beer does. Here’s a table of many of the physical causes of wild beer: too much CO[sub]2[/sub]: too much pressure, not enough pressure, opening the container wrong, too high a temperature etc. It’s not listed, but contamination of the beer or soda can also cause wildness. Proteins, yeasts, dust, or even a bit of powdered charcoal can all make the carbonated beverages go wild. This used to be a big problem for brewerys that shipped their beer in the days before refrigeration. One brewery, Karlsburg I believe, even went so far as to compile a periodic table of the elements, listing each element’s capacity to cause foaming. Carbon dust was particularly good at making beer go wild. Filtration technology, and good quality control pretty much eliminated the problem, but still, a bad bottle slips through once in a while.