Have you considered a vacuum for drawing the gas-water mix through a filter? It would allow you to remove the water without wasting any gas. You just need to find a coalescing type fuel filter like the kind they use for bio-diesel. Like this crude drawing that looks like a two year old drew it... though I did.
It shouldn't be all that difficult, and some of the time the filters are able to be reused by dumping out the water.
If you didn't care to use the fuel filter, you could use the same setup with the toilet paper trick described earlier.