I've searched to see if anyone has made anything like this, I haven't been successful.
In my houses with 2 or more toddlers, it is such a ridiculous thing trying to get them fed. They are very needy sims which would be fine if all the adults didn't try to do something random with the toddlers when they are hungry or need to potty. I know that the toddlers can pull plates of food down for themselves but that is not very realistic for me and a high chair meal isn't always easy.
So I tried to look in the debug menu for the sippy cups (drink) but there are only empty ones. Has anyone made a buyable sippy cup that is filled with milk or juice that the toddlers can keep in their inventory and drink without the help of an adult? I know they can keep one in there but only if an adult first puts them in a high chair and they aren't freaking out from one of their other needs being low.
Ideas?

I don't know about buyable cups, but I had my adult sim click on the highchair and get drink/food for the toddler while the toddler is asleep. I was able to grab a heap of the toddler food/drinks and then I just kept them in the fridge and got rid of the highchair.