It seems a bit weird using the glass bottle item for milkshakes, especially since the strawberry banana smoothie visually uses a regular glass bottle.
My suggestion would be to add a Milkshake Glass item, crafted with 5 glass in a V shape, that is used exclusively for milkshakes (and possibly smoothies if that item is to be updated).

look at splash potions, no need for clutter

Splash and lingering potions are still bottles, that are formed by alchemy. Milkshakes very clearly use a fancy glass, which would make for a nice decorative item on its own and a good basis for future milk-based items (as well as some gameplay logistics; bottles make drinks with effects, glasses make hunger-filling smoothies, giving them a separate recipe makes sense).
I hope the team can reconsider this, though understandably it is a minor detail.