How to purchase premium features of an android app for a group of people?

For a research project we are utilizing an app available in the Google Play Store to collect data. However to do this properly we need to provide all participants with the paid full version of the app. One version would be buying google play gift codes and telling out participants to use them on the full version. However I was wondering if there is any alternative way to directly enable them to download the premium version such as buying the version for the Google play user with email address xy@gmail.com.