Joe
We are not given enough information here.....

personally I would pull the plug.
However - if the tub plug was plugged up and could not be drained by pulling the plug - one would then choose one of the other instruments.
If I was paid by the hour and it did not matter if it took 3 weeks to empty- then I would use the spoon.... LOL
If however it was full of "your special" water - naturally I would use the the cup and make sure as many of my friends as possible could receive a cup or two...
If we were to ship the water somewhere- then of course the bucket.
Neil