The actual and probably only way to refill your energy now, is to simply;
1. Open up Injustice: Gods Among Us and also your iPad Settings. 2. After you feel you need to refill energy from playing, go to Settings. Make sure you have an internet connection as well. 3. Go to Date & Time. Adjust the time to advance 2 hours and turn off the iPad/iPhone COMPLETELY. 4. Turn on the iPad/iPhone and jump into the game. There! Your energy is refilled!
Arkham Batman and BatgirlAdded 2 Jul 2014, ID #4652
This cheat is for people who have Arkham Batman and Batgirl. When you unlock Arkham Batman's super move put Arkham Batman and Batgirl into a team and when the battle begins you will have all 3 bars of energy straight away therefore your first enemy will be knocked out.
Once your energy runs out when your playing just go to settings and put your date forward by a day which will automatically refill you characters energy then you can go back to the right day and nothing will happen to your characters energy. It's so simple.