Tasting your beverage

[macklikescheese]

I had a question about tasting or adding yeast to your beverage. I've seen that everyone says to taste your beverage to see if it is where you want it before you put it in the fridge but how exactly do you do that? I thought if you opened the bottle while it was fermenting, it ruined the process and that it also had a sort of volcanic eruption. I also don't want to disturb the yeast. So, how exactly do you taste it to know if it is where you want it? Thanks for your help!