Step 1: Take the child to Walmart.
Step 2: Tell her you will not buy her ANYTHING. But offer to give her a quarter for the twisty machines if she is good in the store.
Step 3: Shop, check out, head to the exit, and discover that Walmart has gotten rid of their twisty machines (but don't worry, they still have all those stupid claw machines).
Step 4: Walk crying child out to the parking lot and buckle her in the van.
Step 5: Drive to Smith's because you know they have twisty machines.
Step 6: Attempt to enter the west doors. They will not open because they haven't been unlocked yet, even though it's past 9:00 a.m. when they are supposed to be unlocked.
Step 7: Walk to the east doors, go in, then walk all the way back to the west doors where the twisty machines are.
Step 8: Watch child put the quarter in the machine. Cringe at the feeling in your gut that this isn't going to work out.
Step 9: Sigh when the machine eats the quarter and doesn't give a prize.
Step 10: Walk back out to the parking lot to get another quarter from the van.
Step 11: Walk back into the store (good news! At this point you will have been there long enough that the west doors have finally been unlocked!)
Step 12: Rejoice when the kid finally gets a gumball, and it only took you 45 minutes, two quarters, and a half-gallon of gas to make it happen.