i cant, the earliest one i have is when i kill the guy who ownes the strip, and with this save i have finished the game also it is an autosave
That happened to me while exiting the Nuclear test site (and dying of radiation damage upon exiting the building ~and it autosaved

).
You may just have to accept reverting to a previous game. If you are on PC, it might be possible to load the save, and pop open the console fast enough to assign a new value to their dehydration. :shrug:
(or to enable god-mode, and then assign values, or drink water; this messes with achievements I believe.)