Smart Milk is only useful if there is a toddler in the household. The player can select a teen, adult, or elder Sim, and tell that Sim to make Smart Milk for any toddler in the household. The Sim will get the toddler, bring him or her to the Smart Milk unit, and attempt to use it. (Smart Milk can also be given to a toddler who has been placed in a high chair.) If the use is successful, the unit will spin briefly and produce a glowing green bottle.
The Smart Milk in this bottle will satisfy the toddler's hunger, and the toddler will learn faster for around three Sim hours; this applies both to learning toddler skills (walking, talking, and potty-training) and learning general skills such as Logic and Charisma by playing with toddler toys. While the toddler is under the influence of the milk, he or she will be surrounded by a glow.
If the use of the Smart Milk unit fails due to a low aspiration meter, the Sim attempting to make the milk will fumble with the unit, and produce a red bottle. If the toddler starts to drink from this bottle, he or she will spit up and will lose a skill point.
When making Smart Milk, what matters is the aspiration level of the Sim making it, not the aspiration level of the toddler it's being made for.
The effects of Smart Milk have been known to last beyond three hours, and may even linger into childhood.