Mine recently has been not eating properly and so spending more than necessary on food, eating out or unnecessary snacks.
Usually I'd plan my meals in advance so I could buy only the food I need plus one or two treats I want for the week so I could usually keep my food spend below £25 a week. But with constant moving around, not being home, moving home ect my routine has completely messed up and have been eating mostly convenient crap which is more expensive. Oh that and alcohol, couple of crates of beer I can go through quite quickly. But they pile on the pounds so I've decided to stop drinking except for socially which isn't often.
What about you guys? What's your guilty habit that costs you lots of money.