Literally! A study about caffeinated bees, a team of biologists from the University of Sussex set up two feeders containing a sugar solution, adding caffeine to one of the feeders in a concentration that would naturally occur in nectar. They then trained groups of honeybees from three different hives to collect the solution from one of the two feeders as they would nectar from a plant. Observing the bees over a three-hour period, the researchers found that they returned much more frequently to the solution with caffeine than the one without.
Read more here: http://www.theatlantic.com/science/archive/2015/10/caffeinated-bees/410698/