Well, I like coffee, but only espresso, properly brewed and served (and I'll join you for that glass of chardonnay anytime!). And I refuse to enter a Starbucks and order a vendi-verdi, frutta-lappa-cappa, half non-GMO soy, half Tunisian llama milk, gingerbread-flavored cup of yuck with whipped chickpea foam and a cute heart drizzled in cruelty-free cocoa on top, or whatever they're selling these days.
Anyway, starting when my kids were little, we taught them that sodas were not a beverage. They were a treat, like cupcakes, and most people don't have cupcakes every single day or several times a day. They never accompanied a meal, except for an occasional picnic or Fourth of July party. That Walmart ad that shows the mother picking up "dinner" for her family drives me nuts: she buys a rotisserie chicken, a tub of gooey potato salad and a huge 2 liter bottle of Coke. Yay Mom! (not enough sarcastic emojis exist for that). They weren't intended to replace sleep, rest, or proper nutrition. If you like the taste of Coca Cola, fine, have one after you've weeded the garden, as you relax in the shade. If you like root beer, have a root beer float occasionally, as a dessert. If you love 7 Up, have one at a baseball game. Have an iced coffee or tea when you're sitting on your front porch after a long day, just enjoying the sunshine or watching the storm clouds roll in. You get the idea. Moderation, refreshment, and limits.
The problem is not having a soda from time to time. The problem is the relentless consumption of caffeinated drinks every day, several times a day, to start the day, to replace a meal, every time one enters a gym, with every meal, before and after school. I don't think it's an age thing. It's a matter of self-discipline.
And kids do sometimes drink too many, and the caffeine can vary widely, and the caffeine can cause problems with heart rates. And, they're a common "cover-up" - shoplift an airplane-sized or hotel mini-bar sized bottle of vodka, or pour a little out of the parents' liquor cabinet, dump it in the Red Bull, and no one would suspect.
So I didn't restrict it or prohibit it. I simply told them that sodas and energy drinks and coffee and tea have their place. Make sure your son has an awesome water bottle and fill it with water and maybe a little lemon or ginger or whatever he likes. Just educate him on health, not age restrictions.