We put ourselves on a food budget, with an eye toward both weekly and monthly, and then game the shit out of it. This takes some margin, but if you can set your goal where it's actually doable without suffering ... you want PLANNING and following through, not pain ... then you can make it flexible enough to reward yourselves if you stick to it.
I see people do this in ways that assume they are either super human or get off on being punished and I mean, whatever floats your boat, but I like to set it up so that we LIKE the thing, and I think we get just as good of results. So
*ANYTHING YOU ALREADY OWN IS FREE AND FAIR. Eat out of your pantry. Eat your freezer stores. Eat your leftovers. So much winning.
*Anything you can stretch farther, so long as people want to eat it, is also winning. (Do not push any limits as far as food safety and quality; jeez I hope I do not even have to say this ack. YOUR HOME EC TEACHER IS WATCHING YOU.)
*Extra money at the end= eating out AND TREATS