Although here in the Philippines with our Christian majority.
We have something similar to a fast. Wherein it mimicks an event in christ where da followers parade the streets and don't eat meat for 1 week.
I forgot what we called it back in my village but. The event was somewhat skewed.
Since we are not allowed to eat meat for 1 week. People got creative by using a loop hole.
We lived near the sea and its easy to fish. Soooooo we just ate fish during the entire weekend. Philippines has a lot of exotic fruits and veggies too since we have a tropical rainforest climate.
So instead of a week enduring hardships. We just treat it as another festival feast but with a twist.
Muslims fast from dawn (Fajr) until sunset (Maghrib), during which we don't eat or drink anything. It's more challenging than what you mentioned.
Casually playing with dehydration. Ohh nooo.
What about the more physically unfit folks. Asthma or disabled are they exempted or they are required to participate as well.
Of course, there are always exceptions.