I drink Diet Coke when I need a caffeine boost because I don’t normally drink any caffeine: I don’t like coffee and drink herbal tea.
In the last 6 months, I have needed the boost a couple of times.
I don’t feel a need for any other sugar free or no added sugar drinks.
In the past, I tried a few but saw no point. Especially fake flavoured water.
Usually I drink herbal tea (including home made iced ones in the summer), dark hot chocolate (with an insulin shot) when it’s cold or water.