Where's my Butty?: If you do forget your sandwiches it's always cheaper to buy some rolls and ham, make your sandwiches at work and you should even have enough for the following day - Maybe leave you buns in your drawer and ham in the fridge so you don't forget ;)
Cereal Made: Leave a pack of cereal bars in your drawer. If you are in a rush and don't have time to grab breakfast you can have a breakfast bar with a nice Tea/Coffee and it may prevent you from nipping to the snack van for a sausage butty (better for dieters out there too). You can use this method for snacks too. Vending machines are not the cheapest snack bars around.
Use Leftovers: if you have left over bolognaise sauce for example use it on a spud or pop it in a little lasagne.Salad for tea? Put the rest on your sandwich. Curry? That's be a tasty work lunch.
Reward Me: Sign up for a couple of cashback websites. You can get cash for simply shopping on ebay, buying something of an online site and much more. Just go through the cashback site first and watch the pennies roll in.
Bulk Buy: Buying things like cleaning products, pet food, toiletries when there are really good deals on. These things keep forever and although it may cost more initially they will last for ages.
Thirst clencher: Fill a bottle up of water before you leave the house, tap water is free water and if you're feeling parched you've got that H20 on hand.