I think you're fine to have a glass of normal cordial a day, I drink cordial now and it's not too bad, It's never made me put on weight. I just have one glass a day with dinner and drink water most of the time too. I find the more sugar you have the more you want. Don't go cutting out all the sweet things you love all at once or it will be too hard, but little things like sugar in your tea etc, slowly does it bit by bit. ANy little changes you make will make a difference.
Good luck hun, you can do it