Background Rapidly consuming water may offer practical orthostatic hypotension therapy. However, its efficacy across disorders remains uncertain. This study aims to assess the impact of rapid 350‐ to 500‐mL water intake on systolic and diastolic blood pressure (BP) and heart rate (HR) through a systematic review and meta‐analysis. Methods and Results We systematically reviewed MEDLINE and Embase up to June 2023, including randomized controlled trials and prospective cohort studies. Using random‐effects meta‐analysis, we calculated pooled mean differences (MDs) for maximum hemodynamic effects of rapid 350‐ to 500‐mL water bolus consumption. Participants with orthostatic hypotension experienced increased systolic BP (MD, 24.18 [95% CI, 15.48–32.88]) and diastolic BP (MD, 11.98 [95% CI, 8.87–15.09]) with decreased HR (MD, −3.46 [95% CI, −5.21 to −1.71]). Similar results were observed in multiple system atrophy and pure autonomic failure subgroup analysis. Healthy participants showed modest increases in systolic BP (MD, 2.33 [95% CI, 1.02–3.64]) and diastolic BP (MD, 2.73 [95% CI, 1.15–4.30]), but HR changes were not significant (MD, −2.06 [95% CI, −5.25 to 1.13]). Water had no significant hemodynamic effects in patients with seated or supine postural tachycardia syndrome, although standing effects were unassessed. Our data do not exclude water's potential standing effect in postural tachycardia syndrome. Conclusions In patients with orthostatic hypotension, rapid water intake elevated short‐term systolic BP and diastolic BP, with mild HR reduction when seated or supine. Healthy participants exhibited similar but milder effects. However, patients with postural tachycardia syndrome did not experience these changes in seated or supine positions. Further research is needed to evaluate the promising impact of rapid water ingestion on patients with postural tachycardia syndrome in a standing position, which was not addressed in our study.