Q: How do I backup apps?

backup has not changed.  your apps and app data are contained within the backup file.

The apps themselves have never been a part of a backup. Since they live in the cloud-based app store anyway, they are always available for re-download and thus it is pointless to take up backup space with apps. You have always had the option of transferring apps made on the device to your computer for archival purposes but that is distinct and separate from your device backup. See Redownload or transfer your iTunes Store purchases from an iPhone, iPad, or iPod to a computer - Apple Support

App data is part of the backup, unless the app developer does not take advantage of the standard app saves on the iPhone. Not all developers save their data in the standard location that is part of the iPhone's backup. If that is the case, then the app data is not backed up, and there is no way to save it. And, as far as I have read, there is no way to save the data either, unless the app developer has some external site to archive your data in.

Annie5494 wrote:

 

I know what you mean but sometimes the data contained in an app is really important. For instance, I used a shift worker app that is a calendar containing all my appointments and I lost it all in the transfer....

I already told you app data was part of the backup.