A boomer I know once bragged about using fabric softeners a second time because they still had some use after the first. I've never even considering using the stuff.

I once met some hippie-like people who fed themselves exclusively by dumpster diving. Not sure where they got their stuff, but they had a lot of high-end foods (cheese wheels, expensive meats, not-so-fresh produce, etc). They lived in busses, vans, RVs and stuff like that. They didn't have jobs; not sure how they got money for things like clothes; odd-jobs I guess.

Less extreme "hacks": Goodwill, or Ross/Marshalls if you're feeling fancy. Ebay/Craigslist/Offer-up (need to be careful about getting ripped-off, and Ebay isn't as cheap as it used to be). Buy, cook, and eat mostly cheap staples (rice, beans, pasta, etc). If eating meat, you can use it sparingly by cooking recipes that comprise mostly of cheap staples. Budget Bytes has decent recipes. Unfortunately, most people's biggest expense is housing, and there aren't many "hacks" for that. Maybe, get a work-from-home job and move to Wyoming or something

Piracy, some people buy 3 streaming subscriptions for 50€ a month just to watch one show.

Also depending on where you live you could take the supermarket advertisement magazines, they are free and if you live in an area where you can walk to your nearest stores it can actually save some money

I also know an old man who sells vapes, cigarettes and alcohol to kids (he couldn' save up enougth for a good retirement). You'd be suprised how much 12yo actually pay for a vape you can buyat every store for 10€. He once told me he get's his products from our cheap neigthbour country and only pays ⅓ of what he's charging.

Pay cash for groceries. At the start of each pay period, withdraw your grocery budget in cash for that period.

Make sure that you get bills that exactly covers a day each.

Every morning pull out a bill from your drawer, whatever you have in your wallet is what you have for groceries.