Dissolve baking soda into strong vinegar until neutralized and evaporate to make sodium acetate.
Dissolve sodium acetate in boiling flavored water, cherry, green apple, whatever might go well with sour.
Refrigerate boiled mixture for at least one hour.
It can now be allowed to return to room
temperature, packaged, (I was picturing smallish slurpie looking cups with a removable cap for the straw hole), and shipped.
When the cap is popped and the straw is inserted the contents of the cup will instantly crystallize, if it is stirred as it crystallizes it becomes...