For me personally, hydrating makes a huge impact. My water intake in the morning can influence my day well into the afternoon hours. The best thing is, it costs next to nothing and can be done very quickly.
A good way to get into it is to set up a bottle of water on your desk or next to your bed the night before. This way, all you have to do is to open and drink it. Perfect for people like me who are super groggy in the morning.