First you take a few Mentos sweets - the more the better I believe.
Then you put all the Mentos in your mouth, and take a large swig of Coke...
When I think of some of the terrible things other mothers of 12, 15 & 18 year olds have to worry about, I'm so thankful that my biggest worry is how to get Coke stains out of a white sweatshirt!