[pidj]

The pressure washer I have has an alternative tip that, when used, draws the soap from a reservoir to create that foam cannon effect but it's not at high pressure.

There's also this one for a garden hose: https://www.amazon.com/Honest-Wash-Snow-Lance-Cannon/dp/B01MA4WQQA/ref=sr_1_2?ie=UTF8&qid=1494784932&sr=8-2&keywords=Professional+Snow+Foam+Cannon+Adjustable+ Lance+Pressure+Washer+Jet+Wash+with+1%2F4%E2%80%9D +Quick+Connector