Just throwing this out there...

Went to my gym a few days ago and noticed a vending machine dispensing drinks and protein shakes (up to $5-6 / pop). Noticed machine accepts CC and cash, so my internal MS alarm was sounding off. I put a quarter in, then added the remaining balance up to $6 from a CC, then pushed refund, and it spit out dollar bills and quarters! The machine had a Ventech label on it if I remember correctly.

Obviously not the best system and limited to how much cash is in the machine (not to mention COMPLETELY shafting other gym members who actually want to buy drinks and get change back), but could be an idea for some.