There is the option to create custom units of measurement. For example, for a coffee menu item, you wish to count the sugar you use in that drink by the spoonful. Therefore, you may create a custom unit of measurement called spoonful and select the unit of measurement and its quantity that is used in each spoonful.
You can create units of measurement for cups, teaspoons, bunch or any other unit that is not on the default list.
To do this, click on your restaurant logo in the top left, then Settings (gear icon) → Unit of Measurement → New custom unit
Add a name which would be your new custom unit (cup, spoon, jar ect.). Add the quantity and select a unit of measurement from the dropdown list (this is a unit of measurement that is defined in the system).
In the above screenshot a spoon of sugar is 20 grams. You can then select this unit of measurement in a menu item for sugar: