Here we have an example of the Smelling Bottles (part of the Sensorial training). There are two sets of identical aromas and the child smells one and attempts to match it via smell only. This strengthens the child's olfactory sense and also increases interest and awareness in their environment.
The key is to make sure there is no other way to detect the material other than smell. We use a cotton ball as a way to prevent the child from seeing the coffee, cloves etc..