Most are stamped steel or cast iron coated with porcelain. Or they are some type of resin. The resin ones are easy to tell. Rarely you will find an entirely ceramic sink, as they are very expensive.
1. If you find a ceramic sink (I'm not just talking about a bowl, but the whole sink unit), clean it and try to sell it. You may be surprised with what you end up with. People that are rehabbing old homes will pay a fortune for them.
2. There is no need to take a hammer to it. Sell it, scrap it, or curb it. Breaking it only presents a risk of hurting yourself for no benefit.