If you don’t mind getting a new number every time, this is what pay as you go plans for. Just get a new SIM, put some money in it, use it, and just throw it away once you’re done.
Is the point to make it cheaper and not pay for data/minutes etc. when you don't use it? As @ian87w says, this is exactly what Pay As You Go is for... Just top up when you want to. In the U.K. we can get 1 month sim-only deals (don't know if they have them in U.S.) but you're pretty much stuck with it unless you're happy to keep changing your number... And also they will run a credit check every time you sign up for a new contract (even a 1 month one) and that will have a hugely negative impact on your credit score!
Why wouldn’t they? They are the ones offering pay as you go plans, and they get money from your purchase price. You can just buy, use, and throw them away as needed. There’s a reason some call it “burners.” And I don’t think there’s any SIM restrictions in the US, unlike some countries like Indonesia or Singapore.
AT&T Pay As You Go will just stop service if they don't get paid for the next month. You don't lose your number. Then when you pay them again, they flip the switch and you've got service.
Or just go to target and get a ting card. Comes with $40 worth of service for $10. Activate, use for a month or two then throw it away and activate the next one lol. Can probably make it half a year with 30 bucks plus tax.