The obvious way to raise the price by 50% is to cut the amount by a third, selling 4.33oz Cokes.
https://www.reddit.com/r/BottleDigging/comments/1kng6aq/coca... suggests that Coca-Cola was comfortable producing bottles in several different sizes.
Now, a 4 1/3 oz Coke is obviously too small to be worth bothering with. But that's also true of a 6 1/2 oz Coke. These sizes seem more like something you dispense with an eyedropper than something you drink. A normal can is 12 oz! Who'd want to buy a six-ounce beverage?
You can address both problems at once by doubling the price and increasing the volume all the way up to 8.67 oz.