With increased concern for environmental and social issues, consumers and the apparel industry have become more interested in the topic of sustainability. Numerous brands strive to reposition in sustainability by employing credible sources and maintaining information transparency to get consumers’ recognition. By employing the stimulus-organism-response (S-O-R) framework, this study experimented with how sustainability positioning with credible sources (EPA vs. Celebrity vs. Social Media Influencer) and high (vs. low) transparency influence brand attachment, trust, and identification, leading to eWOM and brand loyalty. The findings indicate that sustainable positioning with credible sources (i.e., EPA and Social Media influencers) could achieve consumers’ positive brand attachment, trust, and identification in social media marketing. However, we did not find evidence of the impact of high (vs. low) transparency on these dependable variables. Furthermore, brand loyalty and eWOM are significantly influenced by consumers’ brand attachment and trust, whereas brand identification positively affects brand loyalty only, not eWOM. Additionally, this study found that women and higher-income groups had a high preference for sustainable brands.