What's that bladder thing with the hose the guy holding?
Desert or cooled water bag, hung on bumper or outside rear view mirror [didn't have to stop to retrieve]. It's a rubber bag covered w/ canvas & some just used a cork stopper. Canvas was soaked w/ water & as air passed over bag, evaporation would cool the water.
When Dad would drive the tractor out in the field, he'd fill a gallon jug w/ water & wrap w/ gunny sack around jug then dip in stock tank to soak the gunny & set it in shade of fence row.