Fuel tank cleaning

I am working on a truck that has been sitting since for a few years and had gas left in the tank. What are you guys using to clean old gas out of fuel tanks?

If you are dropping the tank I would car wash soapy water wand blast it out good then a visual & see what it looks like. If no removeal I ain't sure. EDIT A radiator repair shop might be able to boil it in their tank (if EPA regs will still allow that).