Post Offices often do budget food options. Not the healthiest, but:
Broken biscuits on a box*
Walnut-less walnut whips in a bag**
I have seen a pack of Raspberry Ruffles yet cannot be sure if it was discounted or just another weird throwback without the 70s price-tag.
*You most likely will not be able to re-join them, so just enjoy the random-ness. That said, finding a whole choc biscuit amidst the big white inner-bag which contains biscuitgeddon … is the most indescribably triumphant feeling.
**If you actually like walnuts and have spare walnuts then you may actually correct the defective whips. Melt the chocolate on the whip with a lighter (or similar) and smartly affix the 70’s-flavoured nut to the top. I sometimes play a few Devo tunes whilst affixing. Youtube is arguably cheaper than CDs even with the wifi.
Also cook masses of fiid and freeze it.
Use cash not card. Work to a tight budget. Put the weekly shop budget (in cash) in a box at start of the week. If it’s gone it’s gone.