You're barking up the wrong tree.. That's only possible (at that age) if the humidity was too low or the hatch went too long.. otherwise it's not dehydration. Was hatch day 21?
Did the chick hatch on it's own or get helped out? Is it from your own flock?
If you have access to poultry Nutri drench.. that's the superior choice over egg yolk which requires digestion and nutri drench does NOT.
It's too early for pasty butt also.. but make sure the bumm is clear.
If a chick is aspirated (crackling breath sounds) when trying to administer water, etc.. it will not recover.. that's basically drowning. When administering anything to chicks this small.. is best to hold them in your hand with beak facing forefinger and drip just below the nostrils using the bend in your forefinger to help direct them together.. the chick will swallow when it rolls around into the mouth.
Hope that baby starts to thrive!