Soda is total garbage. Your body deserves better. PG pretty much covered it.
Some alternatives to help you kick the habit (and it may be helpful for you to transition through these in the order I give them, say, switch every few weeks or so):
1. Diet sodas. Honestly they're still not great for you, but they are a good first step if you're trying to wean yourself off. For me personally, regular soda is way too sugary. I don't drink a lot of soda but when I do (maybe one every couple months or so) I only drink diet. Non-diet soda tastes gross to me. Tooooo sweet!
2. Iced tea. Get the unsweetened kind and sweeten yourself with sugar substitute or honey (if you use honey, keep a close eye on the portion; honey is way sugary!) Alternatively, use mint leaves.
3. Juice spritzers. Juice is really high in sugar, but if you dilute it with club soda it cuts the sugar but still gives you a sweet/fizzy thing. You could cycle these in with iced tea if you wanted.
4. Lemon-mint spritzers (these are *awesome* on a hot day). Put a little sugar substitute in the bottom of a glass. Squeeze the juice of one lemon into the sweetener and mix until dissolved. Place torn fresh mint leaves in the glass and muddle with the sweetener/lemon mix using a pestle. Fill glass with ice and top up with club soda. Stir and enjoy.
5. Flavored waters. Aquafina's "Flavorsplash" is my favorite. They also have fizzy ones but those have sugar in them. The "still" waters don't. They are sweetened with Splenda. I drink 4-6 of these per day. I suppose some would argue that artificial sweetener is just as bad for you, being all artificial and chemical-y and stuff... and I can't say I disagree with them. However in my case, I have never been one to drink enough water (or any kind of fluids); and these go down really easy for me. I am the most hydrated with these that I've ever been in my life. My doctor is pleased.
Ultimately you want to get to the point where water or brewed iced tea (not the sweetened pre-prepared, sugary fake kind) is pretty much all you drink, if you're worried about your soda intake. Then again, there's something to be said for moderation. If you really, really like soda, go ahead and drink it, but use some restraint. Cut back to one a day or three a week or something. I drink coffee daily and wine 3-5x/week with dinner. Arguably these things are "bad" for me, but I accept that I will have a few "bad" things in my diet and I adjust the rest of my diet/exercise/sleep/overall wellness habits accordingly.
To steal a quote from the South Beach diet: "There are no bad foods, only bad habits."
Hope that helps.
