You are free to bring water if you choose, but that doesn't obsolve the company of their responsibility.
Here's where we disagree. I'm not going back to read all your posts, so I don't know if you are part of the group that wants UPS to supply bottled water to drivers or not to satisfy the law.
For the others, the consensus seems to be that for UPS to abide by the law, they need to supply drivers with bottled water. This is incorrect. They need to supply drivers with water. The water fountains are at the buildings to supply employees with water. Fill your jugs with this free water before you leave. So now this water is not 30 miles away. It is in the back of your truck.
If you have an unexpected long day and did not bring enough water with you, feel free to drive somewhere and fill your jugs again. Any restaurant will fill them for you free of charge. You should only need to do this once on a particularly long day, and this should not happen very often. Do it everyday and you should realize that you need to bring more with you. UPS will not have any issues if you have to do this occasionally. Make it a habit, and yes, there will be issues.
Or do you want UPS to deliver you water throughout the day? I don't know, maybe every half hour or so?
I will not argue the fact that you may have a case to have UPS supply you with the water jugs. This would be a separate issue, although I'm sure there is already a ruling from OSHA somewhere.
the company you work for can't say we have water at our office 30 miles away
The water is not 30 miles away. UPS supplied you with water to take with you and keep in your truck. If you're too cheap to buy your own water jugs, file a grievance to have UPS pay for your jugs. I have no issue with this, win or lose.
But, they are supplying you with water, plain and simple. If you choose not to take the free water with you, well, that's on you.
And for those buildings that supply water bottles, take them with you also. The point is that UPS does not have to supply water bottles to satisfy the law unless the water fountains are not potable. They have to supply water.