Unless your toddler has an allergy, avoid using non dairy milk.
Cow’s milk is an excellent source of calcium and many micronutrients. It is fortified with vitamin D, children who don’t drink it are at a higher risk of developing rickets.
No plant milk has a similar balance of fat, protein, carbohydrates, or calories per serving.
With smaller stomachs than us, toddlers rely on nutrient and calorie-dense foods. Children who drink alternative milks do not grow as tall as those who drink cow’s milk.
In the Case of Allergies
If you need to use non dairy milk for any reason keep in mind:
Goat’s milk is the most similar widely available alternative to cow’s milk
For plant milks, soy has the closest number of calories, and protein per serving when compared to milk
If your child cannot have animal milk there are plant based toddler formulas which are formulated to overcome the nutrient deficiencies of plant milks
Check to see whether or not your milk of choice is fortified with Vitamin D, if not, it can be supplemented, ask your doctor before giving it to your child.
Source:
A Comparison of the Nutritional Value of Cow’s Milk and Nondairy Beverages