If you enjoy a crisp Arnold Palmer, try adding sparkling lemonade for a new take on the famous drink. Meanwhile, pouring in some kombucha will give the tea a mouth-puckering sourness and a boost of probiotics.
Try adding different kinds of sparkling water or soda by coordinating its flavor with that of your iced tea. An English breakfast tea could benefit from the sweetness of cream soda, while an earthy oolong will be complemented by the richness of a cola-flavored seltzer. Use similarly-flavored combinations to intensify the taste; a ginger citrus sparkling water can increase the spicy kick of ginger tea, and citrus tea will become even more tangy with the addition of an orange or lemon-lime bubbly beverage.
No matter the mixer you choose, be sure to add it to your iced tea in no more than a 1:1 ratio. This way you can be sure that you are not overly diluting the flavor of your tea.