if you have anmechanical fuel pump : how about; take the fuel pipe off the carbureter, put the end in your container. next put a tube on the carb and on the other end a small container like a pop bottle. ( make sure it doesn't melt when petrol is applied ) then using some fuel in the container , run the engine and allow the fuel pump to empty the tank for you.
but
IF you have an ELECTRIC fuel pump, put the pipe off carb in container and then just turn the ignition on, no need to run the engine, and it'll empty the tank. ( may need an extra battery and jump leads to assist old battery if it's weak. )