Sugar-sweetened beverages (SSBs) are a major source of added sugars in the diet. A robust body of evidence has linked habitual intake of SSBs with weight gain and a higher risk (compared with infrequent SSB consumption) of type 2 diabetes mellitus, cardiovascular diseases and some cancers, which makes these beverages a clear target for policy and regulatory actions. This Review provides an update on the evidence linking SSBs to obesity, cardiometabolic outcomes and related cancers, as well as methods to grade the strength of nutritional research. We discuss potential biological mechanisms by which constituent sugars can contribute to these outcomes. We also consider global trends in intake, alternative beverages (including artificially-sweetened beverages) and policy strategies targeting SSBs that have been implemented in different settings. Strong evidence from cohort studies on clinical outcomes and clinical trials assessing cardiometabolic risk factors supports an aetiological role of SSBs in relation to weight gain and cardiometabolic diseases. Many populations show high levels of SSB consumption and in low-income and middle-income countries, increased consumption patterns are associated with urbanization and economic growth. As such, more intensified policy efforts are needed to reduce intake of SSBs and the global burden of obesity and chronic diseases. Evidence from cohort studies and clinical trials supports an aetiological role of sugar-sweetened beverage (SSB) intake in the development of obesity and related chronic diseases. This Review provides an up-to-date view, considering the evidence, potential mechanisms and policy actions to reduce the global intake of SSBs. Sugar-sweetened beverages (SSBs) are consumed on a global scale, with intake levels above the recommended daily limits for free sugar in many high-income countries and on the rise in low-income and middle-income countries. Prospective cohort studies of clinical outcomes and clinical trials assessing intermediate risk factors provide strong evidence for an aetiological relationship between SSBs and weight gain and the risk of related chronic diseases. SSBs promote weight gain through adding additional liquid calories to the diet, from hyperinsulinaemia induced by the rapid absorption of glucose, and possibly from activation of the dopaminergic reward system. SSBs contribute to chronic disease risk through weight gain, through development of risk factors precipitated by adverse glycaemic effects and through hepatic metabolism of excess fructose from sugars in SSBs. Several policy and regulatory strategies exist across different levels of governance that can be adopted concurrently to change social norms and limit intake of SSBs among individuals and populations. Given the consistency of the evidence across different populations and high intake levels globally, reducing intake of SSBs is one important step to improving overall diet quality and cardiometabolic health.