The present context investigated the comparative study on the supplementation of antibiotic, probiotic, organic acid, vitamin C, and herbal extract after vaccination into drinking water and their effects on performance, carcass quality, blood biochemical parameters, immune system, and intestinal flora in broiler chicks for 42 days. A total of 420 one-day-old male broiler chicks (Ross 308) were randomly assigned into 7 treatments with 3 replicates (pens) per treatment and 20 male chicks for each replicate (pen). The experimental treatments consisted of drinking water (control, without additive); drinking water + antibiotic sulfamet; drinking water + C-Vet-50; drinking water + antibiotic sulfamet + C-Vet-50; drinking water + probiotic Primalac; drinking water + butyric acid; and drinking water + extract of Echinacea purpurea Moench (coneflower). There were no differences observed among the treatments for feed intake, but during the whole experimental period, the highest body weight gain was found in the chicks fed with drinking water + antibiotic sulfamet + 50 cc vitamin C (P < 0.05). There were no differences (P > 0.05) observed among the treatments for feed conversion ratio (P > 0.05). Moreover, there were no differences reported among treatments for carcass characteristics at the end of the experiment. Among the treatments, drinking water + 50 cc vitamin C, and drinking water + extract of E. purpurea reduced (P < 0.05) the levels of cholesterol, triglycerides, and low-density lipoproteins. Drinking water + 50 cc vitamin C, drinking water + Primalac, and drinking water + extract of E. purpurea increased (P < 0.05) the lymphocytes count and decreased the heterophils count and heterophil:lymphocyte ratio. The highest Escherichia coli count and lowest Lactobacillus count in ileal content of the broilers were observed in the control group (P < 0.05). The additives used in this study may be incorporated in the drinking water of broiler chickens as growth promoters and for improved performance. A further, wider supplementation study is required to understand the performance, immune system, variation in the intestinal microbial counts, and any other possible alteration in the intestinal biota of the broilers.