Well, I figured out a way to make something like homemade club soda:
* Mix water and citric acid
* Add some baking soda
* Stir for a while
It will fizz and get bubbly, and be carbonated.
I imagine you could do the same thing with ascorbic acid (vitamin C) and baking soda, since it reacts, too.
But, if you don't want to drink plain carbonated water with somewhat of a salty taste, you might try mixing baking soda into orange juice, lemonade, limeade or something instead.
Note that the sourness from the citric acid can disappear when mixed with water and baking soda.