Teresa is correct .. it's the maltodextrin filler "deflating".

I experimented with some Splenda in a glass of room temperature water ... it fizzed. To another glass of water, I added some cylamate sweetener that has maltodextrin as the filler ... it fizzed. To a third glass of water, I added some cyclamate sweetener that has dextrose as the filler ... it did NOT fizz.

There's no bicarb in there


Doreen