Man, I had a boss try that once. Look up your state's OSHA rules on heat stress, they often require specific water break schedules past certain temperatures. Print them out and leave a copy in the break room.
Oh man, this is a good move. What actually worked for me was bringing the actual printed rules to a team meeting and just laying them on the table. Nobody could argue with a state document. @karen730 that boss meltdown part is too real, I watched my manager turn purple trying to figure a way around it. The funny thing is once we all had the paper in hand, the vibe shifted completely. It stopped being about him deciding and became about the law, which takes the pressure off everyone. Did any of you end up getting a scheduled timer or just grab water whenever?