Perhaps worth noting that it is possible to teach infants (often starting at around 9 months) sign language so that they can more easily signal their desires.
Some priority recommended words would probably be:
* hungry/more
* enough/all done (for when they're full)
* drink (perhaps both milk/formula and water† gestures)
See:
* https://babysignlanguage.com/chart/
* https://www.thebump.com/a/how-to-teach-baby-sign-language
These are not (AFAICT) 'special' symbols for babies, but the regular ASL gestures for the work in question. If you're not native English-speaking you'd look up the gestures in your specific region/language's sign language:
* https://en.wikipedia.org/wiki/List_of_sign_languages
* https://en.wikipedia.org/wiki/Sign_language
† Another handy trick I've run across: have different coloured containers for milk and water, and consistently put the same contents in each one. That way the infant learns to grab a particular colour depending on what they're feeling like.