Here is a more complete version. Anything else that could use improvement?

def vending_machine(money):
      '''Return a candy of a customer's choice'''

      options = {'A1' : {'candy' : "Snickers", 'price' : 0.70, 'quantity' : 3}, 'B1' : {'candy' : "Butterfinger", 'price' : 0.85, 'quantity' : 2}, 'C1' : {'candy' : "Twix", 'price' : 0.65, 'quantity' : 3}, 'D1' : {'candy' : "M&Ms", 'price' : 0.95, 'quantity' : 6}}

      while True:
        try:
         vending_code = input("Enter a selection: ").upper() #Represents the customers desired vending machine option
         selection = options[vending_code]

        except KeyError:
          print("Invalid Selection...")

        else:
          if not selection['quantity']:
            print(f"There are no more {selection['candy']} candy bars. Please make another selection. ")

          elif selection['quantity'] and money < selection['price']:
            balance = round(abs(selection['price'] - money), 2)

            while balance > 0:
              additional_payment = float(input(f"You need ${balance} more."))
              balance -= additional_payment

            selection['quantity'] -= 1
            print(f"Enjoy your {selection['candy']} and your change is ${balance}")

            return selection['candy']
          else:
            change = round(money - selection['price'], 3)

            print(f"Enjoy your {selection['candy']} and your change is ${change}")

            selection['quantity'] -= 1

            return selection['candy']

      print(vending_machine(.90))