I bought a kayak bilge pump (see, for example,
www.rei.com and type 684985 into the Search box). The body drops right into the opening of my blue Wal Mart 7 gallon water carriers.
After I got the pump, I went to Home Depot and got a short length of clear vinyl hose of the right size to press onto the pump's outlet fitting. Now I don't have to mess with a funnel or lift the jugs. The jugs sit on the tailgate of my Explorer or on the ground beside the TM, I drop in the pump, and in short order all the water is transferred.
Bill