That was pretty lame. A few of those 20 gallon totes in the back of a pickup truck, filled part way with a very soapy mixture (a few bottles of dish soap) and, if desired, some glycerin to make the bubbles last longer. THEN, add in 50 or so pounds of dry ice and go for a ride through the city.
At red lights, the bubbles start filling the bed of the truck. When you take off again, the bubbles start flying out, where they burst giving that little cloud effect.
Remember kids, if you're pulled over, yell "OMG! IT'S REACTING! I'VE GOTTA GET IT AWAY FROM THE POPULATION!!" Make sure you have a friend recording everything for later lols on youtube. He'll have to post the video though, since most police don't have that type of a sense of humor.