Carbonated drinks have an adverse effect on healing and the additives
in them can predispose to the formation of renal calculi, especially
in a kidney that is recovering from an infective insult/
If the infection was persistent, your son would have had frequency of urination even at night.
Do ensure that he has adequate fluid intake 1500 - 2000 ml per day that includes milk, citrus juices, and water. You can always substitute carbonated drinks with lemonade.