The lyophilised sumac (Rhus coriaria L) extract (LSE), in amounts of 0.25, 0.5, 1.0, 1.25, and 1.5 g/100 ml of juice, was incorporated into carrot juice, and its properties were assessed after 24, 48, and 72 h. A product without the lyophilised sumac extract served as the control. The highest supplementation level enhanced the physicochemical characteristics of carrot juice, increasing carotenoid and polyphenolic contents by 22% and 70% on the first day. The LSE significantly boosted antioxidant activity, yielding over a tenfold increase, while reducing capacity was elevated more than sevenfold. LC-MS analysis confirmed the presence of bioactive compounds, such as chalcones, flavonols, flavones, and phenolic acids, further validating the extract’s functional potential. Acidity and redness exhibited a proportional increase with the rising concentrations of the additive used. Additionally, microbial growth, including aerobic mesophiles, yeasts, and moulds, was markedly suppressed. After 72 h, the total count of aerobic microorganisms and yeasts/mould was reduced by 5.64 log and 4.94 log, respectively, compared to the control. The lyophilised sumac extract, rich in valuable bioactive compounds with antioxidant properties, effectively preserved freshly pressed carrot juice, mitigating spoilage and extending its shelf life. This form of sumac serves as a sustainable beverage additive, minimises food waste, and aligns with clean-label trends.