I just started letting my son have gingerale this year, at 3 yrs. He can have it when we go out to eat, or when we are on an airplane. We do not buy any soda OR juice in our house. Ever since I was pregnant, gingerale has calmed my tummy when I was nauseous, so I always get it when on a plane, and the last time we flew, I let him get some too, just in case he felt queesy. When we eat out, if I order tea, then he gets milk, but if I order gingerale, and he requests it, I let him have it. He calls it coke, and I don't correct him.

You can't be overly strict b/c the minute they leave your sight they'll be itching to try everything you don't let them have. I wouldn't be upset if he had soda at a party or something, just as long as he understands that it will never take up residence in our fridge

Besides, he goes through 4 gallons of milk a week, he has bones of steel.
My kids take sips of ours when we have it, but have never had their own. I take that back, I have gotten them sprite before at restaurants when lemonade wasn't an option, but it never gets more than 1/8 drank from it.
Usually, lemonade (especially bottled) and juice have just as much (sometimes more) sugar in them than soda. I used to get my DS lemonade when he didn't want milk. One day at the mall, I got him a lemonade and myself a gingerale. I looked at the label and the lemonade and 10 more grams of sugar and more calories, so I switched with him.

As long as the soda is sans caffeine, depending on the brand, there is no difference between lemonade or juice and soda. Granted you get a few vitamins from some juices, but the sugar kinda cancels out any benefit, IMO.