This is all a
You mark my words UPS will eventually have no other choice but to provide climate controlled delivery vehicles.
Are you familiar with how the rules regarding bathroom facilities shook out years ago? UPS was one of the critical cases that shaped OSHA rulings.
Just as it is not reasonable to expect UPS to provide toilets in each package car (only bldgs.), you might be surprised how OSHA will eventually interpret the hydration rule.
We are a "moble crew". The OSHA rules you see as hard and fast may very easily be interpreted differently than you imagine...
Since drivers can reasonably be expected to travel to the nearest restroom on route (even though UPS is required to provide them in facilities), OSHA could interpret the hydration requirement as being fulfilled by allowing drivers to travel to the nearest place that could supply them with water.
Or perhaps you think the urge to drink water is more pressing than the urge to expel it?
OSHA interprets the rules the way they see fit (sometimes with "pressure" or "guidance" by companies).
Your push for free water misses the mark. Heat in the back of the trucks should be your focus.