The effects may be mild or severe depending on the dog size, preexisting health condition, and the type of fruit punch. For instance, diabetic dogs will have dangerous complications due to the high sugars in commercial fruit punch, while large dogs will need to consume a lot to be affected. First, check for symptoms of gastrointestinal upsets like vomiting and diarrhea. If mild, they’ll subdue after a few drinks of clean water. However, contact your vet if the symptoms are severe or the dog ingested toxic flavors like grapes.