Sipping caffeinated tea throughout the day can help you think more clearly, according to a study published in the Journal of Nutrition;  it can also stave off age-related dementia. When paired with caffeine, L-theanine (a unique amino acid in tea) increases alertness, reaction time, and memory.

In your cup
Keep an electric kettle plugged in at work, and sip oolong, white, green, and black teas throughout the day.

Recipes
Green Tea Smoothie
Tea-Basted Roasted Chicken
Green Tea-Poached Salmon with Braised Spinach