Bonuses such as diamonds can be earned by just entering the promo code of another player or have them enter yours. Promo codes can be acquired by tapping on the lower left on a gear icon and hitting the 'Promo Code' button.
After setting the time ahead at least three hours on your device, return to the game and collect all the water. Close the game but don't minimize the app. Now when you set the time back to normal and open the game again you will have the extra water. This trick can be repeated as many times as desired.