Here’s an easy way to save money:  The next time you’re shopping, DON’T drink coffee.  A new study found it makes you spend more.

Researchers offered 300 people a free drink while they shopped.  Each person got a cup, and could choose between coffee, decaf, or water.  About half of them chose coffee.  And by the end, the coffee-drinkers had spent 50% more money, and bought 30% more stuff.

They think it’s because caffeine makes us more energetic, and more impulsive.  And this seems to back that up:  The people who drank coffee tended to buy far more “non-essential” items that they didn’t really need.  In other words, impulse purchases.