Introduction Sugar taxes threaten the business models and profits of the food and beverage industry (F&BI), which has sought to avert, delay or influence the content of health taxes globally. Mexico introduced a sugar-sweetened beverage (SSB) tax in 2014 and other regulatory measures to improve population diets. This paper examines how policy networks emerged within and affected the development and implementation of the Mexican SSB tax.

Methods This qualitative study analyses 31 interviews conducted with key stakeholders involved in the soda tax policy process and 145 documents, including grey literature and peer-reviewed literature. The policy network approach was used to map contacts, interconnections, relationships and links between the state, civil society and commercial actors involved in the SSB tax. These findings were used to examine the responsiveness, participation and accountability of the soda tax policy formulation.

Results Complex interconnections were identified between state and non-state actors. These included advisory relationships, financial collaborations and personal connections between those in high-level positions. Relationships between the government and the F&BI were not always disclosed. International organisations and academics were identified as key financial or technical supporters of the tax. Key governance principles of participation, responsiveness and accountability were undermined by some of these relationships, including the participation of non-state actors in policy development and the powerful role of the F&BI in evaluation and monitoring.

Conclusion This case study exemplifies the importance of links and networks between actors in health policymaking. The F&BI influence endangers the primary aim of the SSB tax to protect health. The identified links highlight the normalisation of connections among actors with competing aims and interests toward health, thereby jeopardising attempts to tackle obesity rates.