Seriously, just go buy a six-pack at Walmart or wherever. Even the old gas station price is stupidly high. Online Walmart says they are less than a buck apiece if bought in packages:
http://www.walmart.com/ip/Full-Throttle-Citrus-Flavor-Energy-Drink-12-fl-oz-6-count/23788354You know what also tastes like caffeine and citrus? Home-brewed iced tea with cheap bottled lemon juice splashed in. Bam, done. There's your face punch.
How to make a gallon of iced tea at home:Ingredients:
1 gallon water
16 teabags
2 pinches baking soda
Bottle of lemon juice (good for multiple gallons of iced tea)
Take an old gallon jug. Clean it. Fill it with one gallon of cold water.
Pour two quarts of water (roughly) from the jug into a three-quart pot. Cover the pot and bring to a boil.
When it boils, turn off the heat and add 16 off-brand Lipton-esque teabags (one per cup of finished product iced tea). Put the lid back on the pot. Set a timer for 15 minutes.
To the jug with some water left in it, add two pinches of baking soda and one cup of sugar. <Baking soda will cut out any overly sharp tannin taste from the super-cheap tea you should be using.>
Now the timer alarm is sounding. Turn it off. Take the teabags out and dump them in your compost pile or trash can. Pour the super-strong tea into the jug. Stick that jug in the fridge.
Take an empty bottle with a cap. Pour in some iced tea, then pour in some bottled lemon juice (around 10:1 proportions - adjust to taste). This is your new citrus-caffeine drink of choice.
When the timer goes off.