This study investigated the effects of caffeine and taurine co-ingestion on repeat-sprint cycling performance and associated physiological and perceptual responses. In a double blind, cross-over, repeated measures study, 11 male participants (age 21 ± 2 years; stature 178 ± 7 cm; body mass 80 ± 13 kg) completed 10 x 6-s sprints on a cycle ergometer, each separated by 24-s, an hour after ingesting: caffeine (80 mg) and taurine (1 g), equivalent to the amount observed in popular commercial energy drinks, or placebo (maltodextrin ∼1 g) in a gelatine capsule. Performance was measured on a cycle ergometer, whilst blood lactate concentration (B[la]), rating of perceived exertion (RPE) and heart rate (HR) were measured at baseline (pre-exercise) and after sprints 5 and 10. Magnitude-based inferences revealed likely, trivial differences in peak power and unclear, trivial inter-sprint fatigue index after ingestion of the caffeine and taurine supplement. Intra-sprint fatigue was greater in the caffeine and taurine condition at sprint 10 (likely, small) and possibly smaller in sprints 6-9. The caffeine and taurine supplement had a likely large effect on HR at baseline (ES = 0.94) and increases in B[la] after sprint 5 (likely small) and 10 (possibly small). There was no effect of the supplement on RPE (unclear, trivial). Administration of caffeine and taurine at doses equivalent to commercial energy drinks did not improve repeat-sprint cycling performance and appeared to induce greater fatigue within selected sprints, particularly at the end of the trial. This undesirable performance effect occurs in parallel with increased HR and glycolytic metabolic bi-products.