Background: Metabolic disease, including type 2 diabetes, is a major public health concern. Reducing sugar-sweetened beverage (SSB) consumption is a critical target for disease prevention and lifestyle modification. Workplace interventions offer a promising opportunity to address barriers to behavior change while strengthening motivation and self-efficacy. Objective: The authors describe the intervention protocol, fidelity, and #feasibility of a theory-informed brief intervention based on motivational interviewing principles to support reductions in SSB consumption among health care workers. The authors also explore changes over time in proposed mechanisms of behavior change. Methods: Participants (N=314) allocated to the intervention arm of a multicenter randomized controlled trial received a 4-dose intervention consisting of an introductory phone call, a brief counseling session, and 2 booster calls, supplemented by at-home tools targeting stress and craving management. We assessed fidelity to motivational interviewing principles (competence scores) and described #feasibility via session adherence. Finally, we explored changes over time in motivation for change and perceived self-efficacy. Results: More than 60% of enrolled participants completed all 4 sessions, suggesting #feasibility and high retention in the context of a remotely delivered workplace intervention. Health coaches achieved basic levels of proficiency in 2 of 4 competency scores: technical (mean 3.23, SD 0.48) and complex reflections (mean 41.91%, SD 15.17%). Preliminary exploratory findings indicate improvements in motivation for change and self-efficacy over time. Finally, we found that the use of brief mindfulness practices were associated with acute reductions in stress and cravings. Conclusions: This theory-grounded brief motivational intervention may offer a cost-effective and accessible approach for employers to support behavior change related to SSB consumption. Findings from the fully powered randomized controlled trial are needed to determine if the brief intervention can effectively change behavior. This paper establishes the intervention and its framework to inform future implementation. Trial Registration: ClinicalTrials.gov NCT05972109;