Okay yeah that was my first thought
Are you washing under armpits everyday? Or at least wiping under them with a wipe? Could be a yeast infection. I want to say BO at this age is not common but I’m no doctor
If your toddler has BO, maybe it’s central precocious puberty? Any other signs of early puberty? Would be good to ask your pediatrician
I think I would just stick to soap and water on a washcloth. If it is a persistent problem, it may be worth asking your pediatrician about it.