Red bull and Daphnia
The hypothesis that Red Bull drink increases the heart beat of Daphnia is proven to be true.
The invigorating experience and feeling gained after drinking a bottle of Red Bull is probably due to the caffeine in the drink. The actual level of caffeine in the Red Bull drink may not be the same in different countries due to different regulatory controls and laws of each country.
The experiment can also be done by using other energy drinks like Monster.
Try to repeat the experiment by adjusting the room temperature.
Red Bull - http://en.wikipedia.org/wiki/Red_Bull
Daphnia - http://en.wikipedia.org/wiki/Daphnia
Handle all laboratory equipment carefully, wearing safety gear/gloves.