I have had (since 1994 anyway) hard luggage, so "where" to carry it is only a question of the left or right bag, and front or back of the bag.
And no question of what container, just the plastic jug with screw top cap.
One thing I will say, is once open the cap, when putting cap back on, not only put it on tight, but also squeeze the bottle in a little bit before tighten the cap, so if/when the air inside were to heat up, the bottle has some room to expand without building up any pressure to cause it to leak.
And dont tighten so tight that it deforms the threads.
And no question of what container, just the plastic jug with screw top cap.
One thing I will say, is once open the cap, when putting cap back on, not only put it on tight, but also squeeze the bottle in a little bit before tighten the cap, so if/when the air inside were to heat up, the bottle has some room to expand without building up any pressure to cause it to leak.
And dont tighten so tight that it deforms the threads.