A Note About Milk
In India cows are revered as sacred and their milk is a blessing. Cows are freshly milked every day and people drink that milk without processing it. Use whole milk for the most authentic flavor. To cut calories, you can adjust the water to milk ratio to your liking.
I normally drink almond milk, but chai is my exception. You can use soy, almond, rice or coconut milk if you want, but the flavors will not be the same. You may find it delicious, but it will lack the authenticity.
You decide.