Custom field will allow You to save information about clients buying habits, favourite products, services and other specific information. 

Use the data to make customers segmentation(for example, black coffee drinkers), add deposit, add coupons to specific segment of customers or monitor the information and export data to email or Excel.

Create custom field with options to find out customer's favourite drink, buying habits. 

Choose type dropdown to add unlimited count options.

Add specific information about Your client and save the changes.

Select John Smith's favourite drink.

In customer section You can filter data using custom field condition. 

For example, select all customers who like the most black coffee and in Actions add them 2 EUR coupon for next purchase.

In transactions section You can filter transactions using custom field condition.

For example, monitor statistics (in Header) how active were Your customers who's favourite drink is black coffee. In real time measure how effective is Your loyalty campaigns to specific segments.