You have two options :
 

• The VPP Program , also known as the Volume Purchase Program for enterprises, allows you to easily distribute apps that meet your organization's needs via a URL, for example. 
• The Apple Developer Enterprise Program allows you to create certificates and provisioning profiles in order to distribute your apps via an internal portal or URL. 

This article covers alternatives to the Apple Developer Program for enterprises.

With this method, your binary (.ipa file) will be hosted on a server, and you'll give a URL to the users of your choice which gives them access in https. 

Industry trends are moving fast...you may have started to hear the term "Progressive Web App" being dropped more and more often, but still haven't taken the plunge. Don’t be afraid to experiment with your offering in order to provide your clients with innovative and advantageous products they may have not considered before. The recent update to our product represents an opportunity for you to repackage or add to yours–read on for some tips on how to boost to your pitch and results.