This tutorial uses the bowline knot as base to make the jug or bottle sling knot.
The knot can be loosened and transferred from one bottle to another
I started with a 4' length of cord. 15" from the Working End bring said WE over itself.
Bring WE up through that loop leaving a 3" long bight
Bring WE under Standing End
and down through the loop
Bring WE over one strand of the bight
and under both strands of the bight
Bring WE Over one strand, under two and up parallel to the Standing End
Spread the original loop apart a bit
and slip it over the neck of the water bottle
Grab the small loop ion one hand and the two strands in the other and pull the knot TIGHT under the lip of the bottle
Tie the Working End end Standing End together as close as possible to the knot leaving a long bight opposite the original 3" bight
Put the long bight through the 3" bight
and bring it back over itself
Pull on the two strands of the bight so that the end of the long bight snugs down against the 3" bight. The result is a knot that will self adjust by sliding along itself