Soy is an allergen; my son has soy allergy which results in serious eczema outbreaks.
So please go through the usual 3-7 days allergy test by offering small amounts first.
If cleared, can offer more.
Do you plan to wean toddler to soy milk?
If so, then do read up on some potential risks of taking soy regularly.
Although I'm a vegetarian, I still believe that young mammals need to take animal milk protein for better absorption. Best is human breastmilk, then followed by goat / cow milk.
Otherwise, the occasional soy drink or meal is fine.