A while back, my daughter-in-law told me that their cat was throwing up almost daily. Was it the food? Nope. It was the bowl. It turned out they were using an automatic feeder with plastic bowls and were NOT washing the bowls out daily!
Even though their cat licked the bowl "clean," food particles from the food and her saliva created a lovely breeding ground for harmful bacteria. Once the humans started washing the bowls out with hot, soapy water daily, the problem mostly cleared up. (Next we got the kitty on better quality canned foods as well.)
1) Plastic. Plastic bowls can become a nasty breeding ground for bacteria very quickly. Never buy cheap plastic bowls for your dogs and cats to eat or drink from. Are they BPA safe? Does the bowl show scratches from teeth or from cleaning? These grooves in the plastic are a real problem. Recycle them now and replace them with better bowls!
2) Stainless steel Not my favorite choice. I've noticed that folks tend to leave them outside and just rinse them out occasionally. This happens more with the bowls that are weighted and/or have a rubber bottom to keep them from slipping. Stainless steel can get dented and even hold an electrical charge.
1) Lead-free ceramic. Look for heavy ceramic bowls for big dogs or passionate eaters, but be sure that they are not cheap stuff that may contain lead. Good quality ceramic bowls can be thoroughly washed and/or put in the dishwasher.
2) Glass. Heavier glass bowls are a good alternative, PLUS you can easily see if they are dirty.
Plates vs Bowls
Many cats prefer plates over bowls, as bowls compress their whiskers. My youngest, Flora, is a bit of a messy eater, so she eats out of a wide, shallow bowl which leaves room for her lovely whiskers, but It has a lip which keeps most of the food from escaping.
Be sure to pay attention to your pet's bowls and clean them after every meal to avoid illness and infection. Just another simple thing that can make a BIG difference!