The effectiveness of personalized advertising sweets is also based on the principle of reciprocity. It is extremely simple and has been the foundation of successful relationships for centuries. It says that we should reciprocate the person who has done something for us. The idea of ​​reciprocity has its application, among others, in marketing. When a brand delivers something unique and personalized to a customer, it creates stronger emotional connections. Recipients feel appreciated and noticed, which makes them more loyal to the company.