Which folk remedy is largely debunked due to inconsistent efficacy based on diet-related variability in the agent used?

Using human urine.

Scientific literature provides clear comparisons regarding the efficacy of various folk remedies suggested for jellyfish stings, and human urine is largely discredited. The reason for its inconsistency lies in the fact that the pH level of human urine varies widely depending on an individual's diet and hydration levels. Because the effectiveness relies on a specific pH that may or may not align with the toxin or the condition of the patient, applying urine might occasionally result in a positive outcome by chance, but frequently it has no therapeutic effect at all. In some documented instances, it may even exacerbate the situation by causing additional venom release, making it an unreliable and often detrimental choice compared to agents like vinegar.