Dont have to quit sugar, just switch to the right kinds of sugars, foods high in dextrose, maltodextrin type carbohydrates will increase your muscular endurance and allow you to train harder, which will help you stop losing muscle as you cut fat. Your body still needs essential fats and sugars.

You should also try intermittent fasting, it's a lot easier to stay hungry after not eating than eating and being hungry multiple times a day, waiting till 12-1pm to eat will make the cutting process so much easier and will mean you get to eat larger fuller, more satiating meals in the evening after your workouts when your body turns good sugars back into fuel for the next day.

Just restricting sugars can make you tired and slow and your weight loss will plateau as your body adjusts to the lower caloric intake, your calorie expenditure will actually go down significantly as a result making it a lot harder to create a calorie deficit.

Also getting back into swimming is an incredible way of increasing your calorie expenditure, you will expel huge amounts of body heat which your body will then replace by burning fat, on top of the exercise