Can I make a “cake smash” for my child? Basically, when a baby turns 1, you bake a cake and let them smash it. It is a messy way of letting them have fun, and is a unique way of celebrating their first birthday.
There is a prohibition against wasting and/or disgracing food. This is especially stringent in regards to bread or other mezonot-type foods. When there is a legitimate reason to use food for a purpose other than eating, there is room to permit it. However, in this case, it seems difficult to consider this a legitimate use of the cake.
See Shulchan Aruch O.C. 171