dry yeast comes to life once exposed to moisture.
they will quickly starve if no sugar food is around.
it's best to super saturate the sugar into water,
then sprinkle a little yeast on top; no need to mix.
I don't know of any kind of yeast the average person can buy that's not active once mixed with water and sugar, but look for the "active dry yeast" on the side of the package just in case. And check the expiration date as well.