Even if you don't live like the koalas in Australia, you can reap the energizing benefits of eucalyptus leaves from their essential oils. While it's long been linked to treating aches and pains, eucalyptus oil also has energizing benefits. It has been shown that brain wave activity increases when people breathe in eucalyptus oil, alleviating both mental and physical fatigue.
Like eucalyptus, rosemary can have positive effects on the brain, which can help during those times you're feeling fatigued. Studies have shown that smelling rosemary helps with memory and focus.