Go to Apple Market and kick the can into the bakery. The woman behind the counter will give you 1000 Zenny. Enter any shop and exit. The can will reappear. Repeat this as many times as needed. Note: This will still work when everyone leaves.

Go to the market just before the main city (the junk store is found here). At the south entrance/exit, you can find a small yellow can on the ground next to a garbage pail. Start kicking it until you put it behind the counter of the larger of the two bread stores. A "Nice shot! Bonus 1000 Zenny" message will appear, followed by "Remember to recycle your empty cans." You can exit and re-enter the market and repeat this as many times as needed.