Assuming a water fountain is unplugged, non-electric, or somehow operational without any Melachos involved (or one is swallowing rain drops), would one have any problem consuming food or liquid from an area without an Eruv (like Reshus Harabim) on Shabbos?
And does it matter if the person is stationary or moving?
Finally, does it matter if the mode of consumption involves no hands?
SO O Ch 350 (1) says in part and from the source in Eiruvin …
“… one is permitted to stand in the public domain and take a key from the private domain and open a door there, and the same is true from the private domain to the public domain. However, he may not stand in the private domain and extend his head into the public domain and drink there, or the opposite, unless he extends his head and most of his body to the place from which he drinks; because he needs the water, we worry that he will bring the water to himself. However, one is permitted to stand in the private or public domain and drink in the karmelit, or vice versa.”
So it can be seen that a person may stand in one domain and drink there from the water in the same domain (subject to any other restrictions like that of Rav Belsky).
I believe that there is no Halachik problem with drinking in רשות הרבים (public domain). However, you cannot fill a bottle or container with water, or even carry it in your hands for more than 4 Amos.
