Protein Birthday Cake Shake
30g protein, sprinkles, cake-batter flavor — gym-bro dessert.
Inspired by the Fairlife + Jello cake-batter shake trend showing up in the assistant logs. Built on high-protein milk and a scoop of birthday-cake whey for a milkshake that actually fits a macro plan.
Bench-tested by the Will It Slush? team · Last revised August 3, 2026
Ingredients
Scale the batch — amounts update live in your units.
- Fairlife / High-Protein Milk530 ml
- Birthday Cake Whey Protein60.0 g
- Sugar-Free Vanilla Pudding Mix (dry)25.0 g
- Vanilla Syrup (2:1)45 ml
- Rainbow Sprinkles10.0 g
- Water665 ml
Method
- 1.Whisk milk, protein powder, and pudding mix until lump-free.
- 2.Stir in vanilla syrup and most of the sprinkles (save some for topping).
- 3.Run on Milkshake mode for ~50 min.
- 4.Serve in tall glasses, top with whipped cream and the remaining sprinkles.
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Notes from our testing
Whey protein foams in the auger — use a casein blend or accept a head of foam.
Protein powder behaves badly in a continuously turning chamber. Whey isolate in particular aerates as the auger works, and after thirty minutes you can have an inch of stiff foam sitting on top of the mix and a dispensed shake that is more air than shake. Casein and blends foam much less.
The sugar side is easier than expected. Most flavoured protein powders are sweetened with sucralose, which contributes nothing to freezing point, so the powder is effectively invisible to the calculation. Whole milk brings around 5 Brix and you need to top up to roughly 11 with a real sugar — a tablespoon of maple syrup or allulose does it without wrecking the macros.
Run it on milkshake mode. The slush setpoint is too cold for a dairy and protein mix and produces a grainy, separated texture; the warmer milkshake target keeps it smooth.
Sprinkles go on top after dispensing. In the chamber they dissolve within ten minutes and turn the whole batch a uniform grey-purple, which is not the birthday cake effect anyone is looking for.