In a large bowl or a large pourable measuring cup, mix together the chocolate milk and sugar until the sugar is dissolved.
Pour the mixture into the Ninja Slushi machine. Press the Milkshake preset.
Once the machine beeps, dispense and serve immediately. Top with whipped cream and chocolate sauce, if desired.
Notes
Use Boba straws when drinking. Because this produces a thick milkshake, using Boba straws will help you have an easier time drinking it.
Make sure to dispense the milkshake within 30 minutes of making it. Leaving it in any longer may change the texture of the drink.
Start a rinse cycle immediately after dispensing the last bit of milkshake. Sugar and dairy can make the vessel very sticky, so rinsing it quickly will help with easy cleanup.
Use full-fat milk to ensure you get the creamiest milkshake.
Adjust the sweetness to your liking. If you think it is too sweet or are using ultra-filtered milk (like Fairlife) you can reduce the sweetener to ½ cup.