Absolutely disgusting

I work at a church during the week and also occasionally help out on Sundays. Yesterday my class was playing and I noticed that one of the kids was holding and drinking out of a cup that wasn’t his. I took it from him and saw bubbles in it. I opened the cup and quickly realized that the solid that was in the cup was originally chocolate milk. Now this had to have been left on Sunday after service but that milk was so old that it wouldn’t it even come out of the cup when I tried to get the stuff out. This is not the first time that a parent has left old or rotting milk for their child to drink. I get that being a parent is busy but there’s no excuse for giving your child something that can make them sick. The picture down below is what it looked like just more solidified and brown.