Many growlers are made from a single material, like an all-steel growler, or glass, or ceramic growler. Others, especially growlers designed to insulate, are made of multiple materials. Glass and ceramic are often the most affordable, but break easily, and UV rays can penetrate glass and warm or ruin your brew. Look for a growler with a stainless steel or copper liner. They’re easier to clean than ceramic growlers and won’t break like a glass growler. Nor will stainless steel impart any outside tastes or flavors to the liquids.