Can some dishes be washed with only water?

Question

How can you know when washing something with soap is a waste of time?

If a quick rinse removes all residue - is water needed?

Answer 1

Not using standard practice might violate safety standards in a professional context.

Technically, the important factor is whether the residues are made of something perfectly water soluble (sugar, salt, fat-free watery or alcoholic solutions, insoluble but not sticky solid particles...) or of something that is not water soluble and that will adhere to the dishes (about anything containing oils/fats). If you couldn't properly get it off your hands without soap, you won't get it off the dishes without soap.