The International Agency for Research on Cancer identified a possible link between aspartame and a type of liver cancer called hepatocellular carcinoma.
I find the taste of it utterly revolting. it’s like a sweet imposter, and my mouth says, “no!” It tastes somewhat metallic to me. I prefer stevia. although I don’t normally use sweeteners in stuff like coffee or tea. I avoid soft drinks in general, preferring fruit juice if I drink something other than water or milk.
Regardless, the problem isn't the bottle or the freshness. It's that the juice is being processed to remove it from its matrix of fiber and other nutrients.
With tea and coffee, I eschew sweeteners entirely. A well made coffee or tea is delicious without sweetening.
I recently went on a keto diet, and my favorite non sugar sweetener is definitely erythritol plus monkfruit extract. I haven't tried stevia but I've heard good things!