How do you track stock if you sell a bottle by both a glass and a bottle?

[carlystovell]

The only options are item or weight so how will this work?

[Andy]

You can try to use a composite item feature. Composite item consists of other items.

You can make the bottle of liquid as the component and available for sale. Let's name it "bottle." Put option 'Sold by Each' and amount of bottles into 'In stock' field.

Then make other items "glass" that is the composite item, consisting of a bottle of liquid.  Put proportion that glass has out of a bottle. For example, one bottle has 2.5 glasses. So, you should put number 0.4 (1/2.5) in the 'Quantity' field of component "bottle" of the composite item "glass."

Eventually, you have two Items in the sales list: "bottle" and "glass." If you sell any of them, the quantity of your "bottle" item will decrease for the sold amount.

Mor details how to sell liquids like this you can find in the second part of the help article How to sell liquids.