Nowadays, people are focusing on antioxidant-rich food due to its beneficial effect on health. Thus, the goal of this study was to investigate the interactions between catechin, quercetin, and gallic acid in the presence of sugars (sucrose and trehalose) in complex food matrix such as pomegranate juice. Antioxidant activity (AOA) was measured by three different methods, DPPH and ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP). In this paper, fundamental differences among used AOA measuring methods were confirmed, which can be traced back to interactions occurring between phenols and/or sugars. Even though addition of individual phenols increased AOA of mixtures, in the majority of binary and ternary mixtures antagonistic effects were observed. Positive effect of sugar addition was more pronounced in binary mixtures but the results were highly dependent on used AOA method.