I picked up a plastic tank and siphon to drain the Sportster tank.
The process was surprisingly slow and a little tedious. The hose kept curling, which made it difficult to get to all the gas. The siphon kept grabbing air and stopping. After draining about half, I took the tank off the bike. Once off, I attached a piece of metal rod to the siphon tube using some wire to keep it straight and was able to tilt the tank and use the siphon to get almost all of the gas out. Then I removed the petcock and shook the rest out.
Here are two shots with the tank off and the garage door open to vent the fumes.