iPhone does not provide one system-wide button that clears every app cache. The correct method depends on whether you mean Safari website data, downloaded files, or storage used by a particular app.
- For Safari, open its settings and use the history/website-data clearing controls appropriate for your iOS version.
- Open Settings > General > iPhone Storage to see which apps use the most space.
- Inside large apps, remove downloads or cached media when the app provides its own storage controls.
- Offload or delete and reinstall an app only when you understand what local data that action may remove.
Clearing caches is not a general performance cure and can sign you out of websites or cause content to be downloaded again.