## 4 Method  
### Case Study  
The case study is a popular and underrated but at the same valuable research method in social sciences [46], and also in the area of supply chain management (SCM) [47; 48]. Due to the different regional implications, it is also used in the case of SCM or sustainability in FMCG industries [49; 50; 51]. There has also been case study-based research in sustainable marketing and IoE-related literature [52]. Field benchmarks provide valuable insights to the knowledge about IoE and IoT in FMCG industries [53]. However, FMCG consists of many industries, so the case study method is justified only when some interesting, specific, or typical case is described [54]. Moreover, diverse characteristics of possible cases enable the use of the case study method [55]. Nevertheless, the role of the case study method in building theory is undisputed when the research plan is robust [56].  
The research plan was set up based on a few literature sources and consisted of the elements as follows [46; 55]:  
1. Initial source review, defining the exact research problem;
2. Choosing the FMCG industry;
3. Choosing the research method;
4. Designing the expert interview;
5. Recruiting the experts;
6. Conducting the interviews;
7. Analysis of results;  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Criteria** & **Sub-Criteria** \\ \hline \multirow{4}{*}{Technological factors} & Usefulness \\  & Reliability \\  & Cost efficiency \\  & Standardization \\ \hline \multirow{4}{*}{Market factors} & Demand \\  & User acceptance \\  & Business models \\  & Building ecosystem \\ \hline \multirow{4}{*}{Legal factors} & Industry-specific \\  & Consumer protection-specific \\ \cline{1-1}  & Government-specific \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of the most important criteria and sub-criteria in sustainable marketing.  
Preparing the report (paper), including discussing the results and theoretical and practical implications.  
According to the chosen research method, this study is exploratory and descriptive [57]. The reason for choosing FMCG industries, specifically the dairy industry, was due to the daily use of products, the vital role of products in people's everyday lives, and the short lifecycle of products and short shelf life [58]. The other cause of the interesting nature of this industry was its high vulnerability to the changes initiated by the COVID-19 pandemic [59], which resulted from the specifics of the products offered. Because of the changes in supply chains in the dairy industry and uncertainty about the size of the demand [60], even if dairy products are one of the necessities, IoT and its developed form, IoE, seemed to be one of the possible solutions.  
Using IoE technology, several sensors can communicate with a person or other devices and exchange data. In the case of implementing the IoE in the dairy industry (the whole supply chain [61]), the devices are present or will be present in homes (for example, smart stoves, smart TVs, etc.). IoE can be very useful for marketing in various industries, especially FMCG industries, because it can improve the e-shopping market and provide valuable features even for traditional users. The dairy industry is one of the sectors in the FMCG industry that is closely related to people's daily lives, and their maintenance can be subject to the use of smart tools such as smart refrigerators and smart stoves. When combined with digital services, these physical products, besides developing a way of doing things, create an interaction with the consumer. Some of these objects allow the individual to receive customized services.  
These products are among people's daily needs, and therefore their constant presence in the family basket can be significant. For example, most people consume dairy products such as milk, cheese, and butter daily. Using IoE-based systems allows people, e.g., to buy homemade items at the push of a button on cell phones. Therefore, it enables people to save maximum time and money.