First, make a celery-dill simple syrup: In a large pot, combine the celery, dill, water, and sugar and bring it to a boil, stirring. Reduce the heat to low and simmer for 5 minutes. Remove it from the heat and allow the celery and dill to steep as it cools for about an hour. Strain out the celery and dill, stir in the lemon juice, and store in the fridge. This will last for about 2 weeks in the refrigerator.
To make the soda, fill a glass with ice and then add 1 part celery-dill simple syrup, 4 parts carbonated water, and a splash of apple cider vinegar. Give it a little stir and enjoy. If desired, spike it with gin.