How can I transfer apps from a water-damaged phone to iPhone?

You don’t.

if the old phone is not functioning, you can’t transfer anything off of it.

You can restore the new phone from your backups you made before your old phone was destroyed.

Apps that you bought from the App

Store for use on your old iPhone may be in your App Store purchase history, allowing you to re-download them from the App Store.

Any data like photos that existed only on the broken iPhone is gone.

Restore the last backup you made of the old phone to the new one. Anything that was not backed up or synced to the cloud is gone.