I remember once when I was shopping at a large supermarket and thought I'd get a bottle of flavoured water. When I noticed they all contained aspartame, I decided to avoid these drinks. And I have.
So what is aspartame? It is an artifical sweetener that is still used in the UK, despite concerns about its toxic effects on the body. Even small amounts taken regularly can impact negatively on one's health.
Aspartame can be found in sweets, drinks, prescribed medications, over-the-counter medications, supplements, and many other foods.
Some of the newer sweeteners are not much better. And many of these are found in "diet" versions of soft drinks.
It's best to read the label. That is, if you want to avoid aspartame.
And if you're wondering what research studies about aspartame have found, go here.