I assume that you refer to Thing > Product
Product is defined as:
anything that is made available for sale — for example, a pair of shoes, a concert ticket, or a car.
In e-commerce world anything that is made available for sale is called SKU (stock-keeping unit) and product is usually a container for SKUs (I said usually, as different platforms can have different terms or data structures).
So from your description I see that your system has a product which is "A bottle of Coca-Cola" with two SKUs:
- 1-litter bottle of Coca-Cola
- 0.5-litter bottle of Coca-Cola
I would use information of the SKUs for schema.org
Product.
Some schema.org
attributes comes from parent product (in your case A bottle of Coca-Cola) e.g. url
(assuming you have two SKUs: 1-litter and 0.5-litter on the same page) or description
(assuming you have generic description coming from product). But some other attributes like weight
(or size
/ price
) will be specific for each bottle. There is also sku
attribute which usually refers to your SKU number.
As a side note, you can find similar challenge when building, say, Google Product Feed, and the similar approach will work perfectly fine.
I hope that will help.