There’s a coupon-y program at HyVee (grocery store) I frequent that has a cents off gas, max 20 gallons.
It’s bothered me for a long time I couldn’t maximize the value of this, only having a 16 gallon tank, and only realistically being able to push it to 15 gallons filled. I also spent way too much mental effort coordinating and bothering to try to run my tank down almost empty when near one of the participating gas stations. (I end up north of Milwaukee about once a week, which is ~100 miles from the nearest participating gas station).
The solution was obvious (like most solutions once you know them): buy a 5 gallon gas can.
Its also super satisfying to see a $6.38 charge for 20 gallons of gas, although whether it was ~20 cans of free soup, or nearly free gas, depends entirely on perspective.