Motion Sickness Pills
Motion sickness pills were handed out to army troops aboard ships as well as paratroopers and glider borne troops.
The pills contain sodium amytal which is a known sleeping medication. In small quantities it can be used as a tranquilizer to make you calm and therefore not nauseous.
There are a lot of stories of paratroopers falling asleep on the planes and on the ground once they had landed.
In essence the pills where handed out to lower the adrenalin levels of the troops, so they would not freeze in the heat of the moment.