You will need:

2 people, including yourself.

Adequate money.

What to do:

Dont appear to be in cahoots with each other, meaning you dont know each other, and have one person walk into a supermarket and another well out of site. The first person buys a 4 pack of energy drink, be it Mother, V, Redbull, whatever. They then walk towards the other person and hands the receipt over. The next person then walks in, picks up something like a pack of gum or chips, and grabs another box of energy drink, and when at the counter claim that they had bought it earlier and just wanted to get some chips/gum, make sure to make the receipt noticeable. Now you just got 2 4 packs of energy drink for half the cost. Your friend pays you half of what its worth and they keep the other 4 pack, so now you both saved half the price.

Does it work?

Yes. Just don't be idiots and have both in the store and both look like you know each other. Try to get more people in on it, but 2 is most preferable.