It is the sugar in fizzy drinks that adds pounds on. Many people went to Diet colas when they became available in supermarkets and this has eliminated a lot of easy sugar calories. However, calories are calories - they count wherever you get them! I'm pretty sure 'squash,' if you're talking about the drink, has sugar and therefore calories. Am I right? What does the nutrition information on the bottle say?
Soft drink sugar calories don't pack a bigger wallop than other calories. It's just that it's so easy, quick and cheap to drink down those calories. If you drank orange juice all day, you'd be getting plenty of sugar, too, and that means calories!
Fitday has the food log for tracking what you eat AND drink. Put in the amount of food or beverage that you eat or drink in a day and you will see at the end of the day how much the total is. You lose weight by eating fewer calories than you expend.