Large Tea Refills
At my local movie theater, you could get a small drink for $2.50 or a large drink for $3.50, and large gets unlimited refills. Or you could get a SoBe tea for $2.50. But they didn’t give you the SoBe bottle because they wanted to avoid any broken glass incidents.
So they poured the SoBe into the large cup. Boom: unlimited large drink refills. I saved several dollars that way.
Story credit: Reddit / r2d2sthirdleg