Depends on the reason and what you find most motivating. Addiction is tricky and it’s rarely just one thing. Caffeine is physically addictive but there’s also psych and lifestyle aspects to it.
If it’s about the caffeine, try switching to coffee or tea. If you want to go cold turkey, caffeine withdrawal peaks at about three days with symptoms lessening to minimal after about nine.
If it’s a convenience thing, try keeping a water bottle on you and just drink that. If you find water too boring or your local water tastes bad, try it carbonated and/or with a twist of lemon or other fruit. I’d suggest avoiding places where they serve it, but that’s near impossible. You could take note of what situation you’re in when you tend to do it, and try to rejig your routine around that. You could also not keep it in the house; it’s a lot easier to not put it on the shopping list than resist the temptation when it’s right there. Then there’s health and money. Of course you know they’re not great for you so I’m not going to harp on that, but you could try focusing on it more (but try to frame it in a positive way; not “ugh soda is bad”, but rather “hey drinking water is good!”), or give yourself a goal to save up for purely with what you save on soda.
There’s a couple things at play here.
Firstly, the math. Nutrient requirements in a given population tend to be normally distributed (there are a couple that aren’t). RDA is considered enough to meet the requirements of 98% of people. EAR (estimated average requirement) is the middle of the bell curve, so most people’s actual requirement will be closer to that. RDAs are used for diet planning in individuals though, so as to minimise the risk of deficiency. There’s a huge margin of safety between EAR and anything that would cause problems from excess (e.g. Vitamin A toxicity) so using RDA won’t cause issues there. Actually working out an individual person’s requirement for a specific nutrient is a bunch of really complicated biochem, so it’s easier and safer to just aim for the RDA in that context.
Secondly, RDA is kind of a misnomer. You don’t actually need to eat that every day, because the body stores and uses a lot of nutrients as needed. It’s really supposed to be used as more of an average over time. This is why it’s important to eat a good variety of different foods within the main food groups. Meatless mondays don’t cause you to instantly collapse from iron deficiency.
Third, there’s a commercial aspect to it. Food manufacturers love using RDA because it lets them imply their product is healthy, and they love it when public health messaging is “eat more X” when X is a major component of whatever they produce, or something that’s cheap to fortify (e.g. iron fortified cereals). This way they can encourage people to freak out over “oh no, I need this product or I won’t hit my RDA!” Really, most people better off eating generally healthy (roughly 50% fruit and vegetables, 25% protein and 25% whole grains) with a good variety of foods than aiming to hit the RDA of everything, every day. There are a few caveats to that for certain nutrients in some circumstances, but on the whole, no. You don’t need to hit your RDA every day, but it probably should average out over a week or so.