You could have a glass or two a day, but you must count the carb grams. Try to stick with water. I know it's tough - I hate water - but what usually works for me is to ask myself: am I thirsty, or do I want something sweet to taste? I'm usually just thirsty, so I go with water. If I really want the flavour of diet pepsi or crystal light, I'll have some.

A minor problem with those drinks is that they cause sweet cravings in many people.

Best of luck!