How is it possible that I have not made one of these before?
Based on the well known Diet Coke & Mentos experiments… just do a search for “diet coke mentos” on YouTube.
What an easy way to waste 30 minutes…
… but this does seem like a fun father/son outing at some point. Here is a nice web page on the science behind the Diet Coke/Mentos geyser effect.