Squirrels are wonderful, cute and very interesting creatures but they have it rough on nature just as all animals do. I had the fortune to be able to take care of one and it made me realize how good it feels that they exist and that we are able to help them. Once they get used to you they will enjoy your presence and you will enjoy theirs as well. I will share my story taking care of some wild animals for context, if you want to skip this you can go to the text that says "Instructions".
Most people seeking help in taking care of a baby squirrel might be watching for YouTube or websites telling you what to do and honestly the vast majority of sites repeat the same stuff. They say that you should give the baby to a veterinarian, wildlife rehabilitation specialist, you should feed the baby cow, goat, suplementary, electromagnetic or quantum milk, among other stuff. In short, they confuse and don't follow a minimal way to be able to keep them alive. And I say minimal since the place and conditions in which I live aren't the best to find help from other people (out of the city) or find weird products that might cost too much (low number of stores/high prices/low money).
In my case, at first, I had encountered 2 baby squirrels without knowing they were baby squirrels (very baby ones, without fur) and my parents and I even thought that it was probably some kind of alien. Anyways, I could not find at the moment images of squirrels of that age but they, in all honesty, look horrible when they are very young (good thing they get better with age). Still, they are cute.
From these 2 baby squirrels 1 was already dead (I feel bad because I did not dig a hole for it) the other one was fighting agaisnt ants biting it (baby squirrel skin is very thin so be careful with cuts). I tried using a suplementary milk called "Nutri-Milk" (labeled to replace puppies, cats and bunnies milk) and the inmmediate thing that always happened with it is that the baby's poop was of an abnormal color (poop has to be of a very black color to verify that the food being feed to it is actually good for the baby). After a few days of not knowing what to do, the baby died as well because of an internal bleeding, through the skin it was able to be seen and also the poop had red on it (as far as I can tell these babies cannot tell when to stop taking milk so be careful with overfeeding, however the bad milk could also be the issue). Previously we took care of 2 wild bunny babies and we gave then that milk (as well as goat milk) and they also died in a very strange way (they started panicking, and they looked like they lost control over their body and finally stayed without moving until they died). We always had our doubts on the milk given to these creatures and we were always trying to think on something better that should be given to them. A third baby squirrel came by and we did the same with the milk, the squirrel presented the same abnormal poop color with and it died as well. After this it is obvious we were all frustrated and sad.
One day in the night I found a baby squirrel that my dog found (basically my dog finds baby animals and bring them to me alive and well). And it was a squirrel that had fur and had one eye open already (this happened after a strong storm). The baby wasn't moving and what we saw in the moment was this video (the squirrel in the thumbnail of the video is almost the same as this squirrel found in terms of size and fur). The video says some stuff that is important to know (poop color also) so it is good to watch it (remember however that milk might not a very good thing to try with these creatures, specially processed/artificial milk that you don't know with which stuff is composed). In the above video the guy emphasizes in hidrating the animal before making it eat something else and that it is better to let the squirrels not satisfy their hunger to avoid overfeeding as that can be very bad for them.
We were searching for a better milk for this squirrel only to find out that it costs too much or it does not exist on the country. Then, because of some article/doctor that said all the "benefits of egg in the brain", we decided to feed (after hidrating it first) the squirrel the yellow section of the egg (without the container of said yellow section) mixed with a little bit of an electrolite (a powder electrolite used for medical stuff, pediatric can work as well as far as I know). The squirrel took the solution with interest and drank it all (we were very surprised as the milk we gave to the other animals never interested them). The best part is that the poop was also black as it was supposed to be (EUREKA!). After that the squirrel grew, opened its other eye, started eating solids (the first thing he ate was a mango, he was tired already of the yolk + electrolite) and he always loved the sunflower seeds (I eat them too).
This squirrel lets us confirm several things, the first one, all milks were shit , you can solely rely on something very easy to find to feed them, eggs (or at least easier to find than an artificially made milk), and that we can indeed take care of these beings. Keep in mind the squirrel already had fur and an eye opened, but if we encounter more squirrels of very young age we will be applying the egg + electrolite method and the sunflower/mango/tomato method when it can eat solids (they also drink water).
In honour to Bean the squirrel, Patton and Otis the bunnies, 3 baby bunnies and 3 baby squirrels.