This study investigates the influence of mineral water bottle thickness and shape on consumer psychology and behaviour. It explores the influence of bottle thickness-shape synergy on consumer decision-making, fills the theoretical gap of multi-parameter interactive design, and provides an optimisation basis for the global bottled water industry. Thirty college students were recruited to test the perceived value, purchase intention, aesthetic evaluation and comfort level of six design combinations, and the main effects and interactions between thickness and shape were examined by multifactor analysis of variance (ANOVA). Streamlined shapes performed significantly better than geometric shapes in all dimensions, with 0.4 mm streamlines providing the best comfort, and the shape-thickness interaction significantly increased purchase intention; geometric shapes were the least comfortable due to angular design. It is suggested that streamlines (0.3–0.4 mm) should be preferred, while geometric shapes need to be improved in terms of angular or non-slip design, and the study can be expanded to include diverse groups and environmental attributes in the future.