When a group of people or a couple use cronometer they have to add many custom foods but I did not found any possibility to share the custom foods with friends etc.
Is there any ? How do I do it ?
You can share with other Cronometer Users by using the Sharing function in the Profile screen. From there, you can add friends by sending requests by using the email address they registered with Cronometer (I believe that's correct). The friend will receive the request and approve or deny. Once that has happened, you will see their email address listed as type "Friend", and are able to see their foods and recipes when you look at Custom Foods/Recipes.
This is actually a neat little function that I recently experimented with. I need to look at it a bit more, but it was fairly easy to set up.
Hope this helps.