To do this, we will use the APKShare utility, which allows us to extract the APK file of already installed applications and share it. We do NOT need Root.

1. Download the app at the Play Market.

2. Install APKShare and run it.

3. Select the application whose APK file you want to share, click on it.

4. In the window that opens, select how you want to share this file.

You can also download this utility at Github or F-droid.