How to lose weight in 24 hours?

No good reasons: There are no good reasons to lose weight in 24 hours. That time frame is too short. People lose weight through changes in their lifestyles over weeks, months, and years. If doing sports, overnight weight loss will cause weakness, usually due to mild dehydration and unbalanced minerals. A 24-hour fast, drinking just water or Pedialyte, is ok in healthy people (but will feel weaker the next day).

In 24 hours: you would likely be talking about temporary reduction in weight due to water loss. You won't have meaningful loss in that period of time.