Currently, the growing demand for non-dairy functional foods leads to the constant development of new products. The objective of the present work was to obtain a soy-based fermented beverage employing the strains Lactiplantibacillus plantarum CIDCA 8327 or Lacticaseibacillus paracasei BGP1 and to analyze the effect of post-fermentation addition of inulin on the bacterial resistance. Also, the antimicrobial and antioxidant activity of the fermented soy-based beverages were analyzed. The soy-based matrix was shown to be a suitable substrate for the growth of both lactic acid bacteria, and the fermented beverages obtained presented bioactive properties such us antioxidant activity and bactericidal effect against pathogen microorganisms. The addition of inulin after the fermentation process avoid the hydrolysis and so, preserve its polymerization degree and thus the potential prebiotic effect. The soy-based fermented beverages containing inulin showed higher bacterial viability during refrigerated storage. Also, the addition of high polymerization degree inulin to the beverage obtained by fermentation with L. paracasei BGP1 increased the tolerance to simulated gastrointestinal conditions of this strain. Finally, the strain L. plantarum CIDCA 8327 exhibited the best performance in the growth rate, antimicrobial activity, and viability in the fermented soy-based beverage developed also the survival after gastrointestinal treatment. These results may result attractive considering the possibility of using, together with inulin, novel strains potentially suitable for the development of functional non-dairy products, contributing to diversify the type of agri-based food products.