The baking soda test

I'm a little curious about this. I'm not sure I believe it at all. I would think it would fizz up no matter what. But I'm dying to know the gender and have done everything else so I think I'm going to tru this too. So I have a few questions

Does it need to be with FMU or does it really matter or do you think holding it for a few he's would be okay?

Is baking powder the same thing as baking soda? Do you think I could use that?

What are the results? Is fizzing a girl and flat a boy? Or is it the other way around