Tools:

Cheat Engine
Firefox

Steps:

Go to Cityville 2
Open Cheat Engine
Select -plugin_container.exe(firefox) or FlashPlayerPlugin_11 (Watch: how to find correct process for google chrome - Click here)
Value Type '4 Bytes' to 'double'
Scan your current amount of energy Ex. 25
Use 1 Energy
Next Scan 24
Click the 1st address, Hold Shift and then click the last address.
Click on the red arrow.
Change all the values to any amount that you want ex. 100 (TIPS: Select 1 address below. Hold Ctrl +A and then hit Enter key)
Use some energy and then reload the game.
HAVE FUN!!