If you mean diet lemonaid, bitter lemon, Fanta, that sort of thing yes you can but it's fairly icky!
What you need to be mindful of is that anything containing "real fruit juice" will contain natural fruit sugar.
Manufacturers often hide it by using its real name which is fructose but it's still a form of sugar which converts into glucose once it's inside you and the higher the fruit content the higher the fructose.
Some fruit juices also have added sugar as well, it's a minefield!