As another person suggested try to substitute with something similar.
It doesn't have to be purely fizzy water, I used to mix seltzer with a little pineapple juice. Pick whatever you like and start there, you might eventually appreciate just the seltzer on its own and not need the juice.
Just try not to replace a ton of sugar with a ton of sugar, so even with the fruit juice 1/2 & 1/2 would be a start as opposed to 3/4 juice 1/4 seltzer, the opposite of that of course being best.