In the mobile version of NBA 2K16 on mobile platforms (iOS and Android), players have the option to play as (or against) a European basketball team.
Here's how to add European teams to your game:
In the game's main menu, choose "Quick Game."
In the Quick Game menu, touch the arrow next to "NBA" above either team choice.
This will switch from NBA teams to Euroleague teams.
Once you've selected the teams you'd like to play, be sure you're controlling the team you want to (to do this, select the court beneath the team you'd like to play as).