It sprays sudsy water all over the car. So does a rag in a bucket with water and some car wash soap. The foam cannon needs a pressure washer. A pressure washer needs gasoline. A bucket needs nothing. Why use something so labor and capital intensive when a plain old bucket does the job?
The car still has to be washed with a rag. The foam cannon guys sell a mitt with noodles to wash the car. It’s nothing but a fancy rag.
Here’s how I learned to wash cars 65 years ago. Wet the car. Put some soap and water in a bucket. Wipe the sudsy water all over the car. Rinse with regular hose water. Dry with a turkish towel. No need to buy a pressure washer or a foam cannon to spray the car with sudsy water. Savings: About $500.