There aren’t any special instructions on how to clean a foam cannon. Common sense usually applies, but there are a few tips to help you out.
Make sure that the thread of the bottle or foam container is clean after you’ve done using the cannon for the day. Soap can accumulate over time and cause the threads to slip. While the inside of the pipework is self-cleaning due to the pressure moving through it. Make sure to clean the brass on the outside. Use a non-abrasive cleaner, or just use a lot of water to get rid of all the soap. Once everything is nice and clean, make sure that both the bottle and the cannon are completely dried out.