BACKGROUND: Current evidence on the relationship between beverage intake and cancer risk remains inconclusive. OBJECTIVE: This study aimed to examine the association between the intake of 11 beverages and cancer incidence and mortality, with a particular focus on coffee and tea, categorized by their sugar content. METHODS: This large prospective cohort study included 189,020 participants from the UK Biobank. Multivariate Cox proportional hazard models were used to assess the association between beverage intake and the incidence and mortality of overall cancer and cancers of various systems. Additionally, the study investigated the effects of substituting one beverage for another and explored potential mediators underlying the relationship between beverage intake and cancer outcomes. RESULTS: Over a median follow-up period of 8.8 years, consuming more than two cups of unsweetened coffee per day was associated with reduced overall cancer incidence and mortality. Compared to no intake of unsweetened coffee, the hazard ratios (HRs) were 0.95 (95% confidence interval [CI]: 0.92-0.98) for overall cancer incidence and 0.89 (95% CI: 0.83-0.96) for overall cancer mortality. Similarly, consuming more than two cups of unsweetened tea per day was associated with reduced overall cancer incidence (HR: 0.94, 95% CI: 0.92-0.97) and mortality (HR: 0.84, 95% CI: 0.79-0.91) compared to no unsweetened tea intake. Substituting unsweetened coffee or tea for other beverages was associated with a 1% to 5% reduction in overall cancer incidence and mortality. The association between unsweetened tea and reduced cancer risk may be partially mediated by inflammatory markers. Notably, the sugar content of coffee and tea had the most pronounced effect on the risk of respiratory system cancers. CONCLUSIONS: Beverage selection significantly impacts cancer incidence and mortality. For cancer prevention, unsweetened tea or coffee may be the optimal choice.