Make it yourself
Fast food may be cheap compared to restaurants, but it adds up. If you have a kitchen accessible and can handle the task of boiling water, grab a coupon book and start clipping.
If you're busy and don' t have time to cook every day, whip up a couple meals like chicken or pasta over the weekend, plop them in tupperware containers, and stick them in the fridge. Later in the week, the "fast food" will come in handy. Keep in mind it only saves you money if you eat it all.