You're better off drinking coffee, not only is its caffine amount less, but its healthier. I know it's an accquired taste, but one that is worth it imo.
1$ energy can > 4$ coffee ):
Coffee is cheaper if you make your own. Of course it's more expensive if you buy from cafes and starbucks.Invest in a thermos, make a thermos full of coffee and take that with you.
that homemade coffee is yucky though and leaves a really gross bitter taste.
Get better beans. Get full beans and a grinder.
I dislike how it tastes, and frankly it's awful to drink it regularly.
You'd have more money if you stopped buying energy drinks every day.