cup sleeve       
noun [ C ] uk/ˈkʌp ˌsliːv/ us/ˈkʌp ˌsliːv/
 杯套
a tube-shaped piece of material that is put on a cup for hot drinks, to stop you burning your fingers when you hold it
  We use cup sleeves made from recycled cardboard. 我们使用由回收纸板制成的杯套。 
 Synonym: zarf
 - More examples
 - The company gives customers a discount when they bring their own reusable cup, and uses corrugated cup sleeves made from recycled fiber.
 - These reusable cup sleeves are made from textured silicone for easy grip.
 - You could make themed bunting and even coffee cup sleeves!
 - Perfect for use with hot drinks cups, our cardboard takeaway cup sleeves stop fingers being burned.