There are systems that attach to the fuel rail and run a substitute fuel, with lots of detergent, for 20 minutes. Or you can buy a good quality bottle of detergent and drive around for a tank. Or try two bottles.
After the "machine" change your oil. Lots of the "detergent" will end up in the oil and you don't want to carry that around until the next oil change.
What does it? Does anyone do it?