just make sure its no more than halve the neck
otherwise you get an ice plug
and if its fizzy juce you get the gas
fizzing through the plug
and when you thump it will the blunt end
of a wooden spoon you get a mini exposion
and a small shower of ice quite dramatic
but safe [ive been doing it for 15 years
if you want to avoid an ice plug
just raise the cap end by an inch
even if the bottle is full and freezes
solid they will come to no harm
but you cant drink it till it thaws out
quite a lot
oohh and a word off warning
only do it with plastic fizzy pop bottles
not glass or tins
they will explode