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The aim of the study was to investigate in vitro the antibacterial activity of 8 commercial drinking water additives against major zoonotic poultry pathogens (<i>Campylobacter</i> spp., <i>Escherichia coli</i>, <i>Salmonella</i> Typhimurium, <i>Staphylococcus aureus</i> and <i>Listeria</i> spp.). We tested two essential oil-based phytogenics (Phyto CSC Liquide B, AEN 350 B Liquid), two acid-based eubiotics (Salgard^® liquid, Intesti-Flora), and four blends of essential oils and organic acids (ProPhorce^TM SA Exclusive, Herbal acid, Rigosol-N and Eubisan 3000). The antibacterial activity was determined by estimating the minimum inhibitory concentration (MIC) using a microdilution method. The MICs of the products against <i>Campylobacter</i> spp. ranged from 0.071% to 0.568% <i>v</i>/<i>v</i>, in which Herbal acid, a blend rich in lactic and phosphoric acids, also containing thyme and oregano oils, exhibited the highest efficacy (MIC: 0.071% <i>v</i>/<i>v</i>) against all the tested strains. The MICs of the tested products against <i>Escherichia coli</i> ranged between 0.071% and 1.894% <i>v</i>/<i>v</i>. Specifically, the MIC of Rigosol-N, a blend of high concentrations of lactic and acetic acid, was 0.142% <i>v</i>/<i>v</i> for both tested strains, whereas the MICs of Intesti-Flora, a mixture rich in lactic and propionic acid, ranged from 0.284% to 0.568% <i>v</i>/<i>v</i>. The MICs of the products against <i>Salmonella</i> Typhimurium were between 0.095% and 1.894% <i>v</i>/<i>v</i>. Specifically, the MIC of Eubisan 3000, a blend rich in oregano oil, was 0.284% <i>v</i>/<i>v</i>. The MICs against <i>Staphylococcus aureus</i> were between 0.142% and 9.090% <i>v</i>/<i>v</i>. The MICs of Phyto CSC Liquide B, which is rich in <i>trans</i>-cinnamaldehyde, were between 3.030% and 9.090% <i>v</i>/<i>v</i>, showing the highest MIC values of all tested products. Finally, the MIC values of the tested commercial products against <i>Listeria</i> spp. were 0.095% to 3.030% <i>v</i>/<i>v</i>. The MICs of ProPhorce^TM SA Exclusive, a highly concentrated blend of formic acid and its salts, were 0.095–0.142% <i>v</i>/<i>v</i> against <i>Listeria</i> spp., while the MICs of AEN 350 B Liquid were between 0.284% and 1.894% exhibiting high <i>Listeria</i> spp. strain variability. In conclusion, all the selected commercial products exhibited more or less antibacterial activity against pathogenic bacteria and, thus, can be promising alternatives to antibiotics for the control of zoonotic poultry pathogens and the restriction of antimicrobial-resistant bacteria.