Skylar notices Eldon ordering a drink in Hidalgo's which she comments is "a lot of milk". Such a statement leads to Eldon's explanation that it is his lucky drink which he drinks two weeks before big competitions.
The drink consists of: cow milk, rice milk, goat milk, almond milk, coconut milk, and soy milk. When Eldon orders it from Hidalgo's in "Today I'm Getting Over You", the drink is in a paper black and white cup that bears the Hidalgo's logo, with a cap and straw. It is unknown what the actually drink itself looks like, but considering that it consists of multiple types of milk, it is presumably off-white in colour.