I regularly eat ready meals, for the same reason you do. Not too often though - maybe once a week. You just have to pick and choose very carefully.
Forget 'sugar', you need to look at 'total carbohydrate'. Sugars are just a form of carbohydrate.
I allow myself between 20g and 50g of carbohydrate per DAY, because I eat a low carb diet. I will occasionally allow myself up to 70g. So - today I have eaten a 2-egg omelette for breakfast, maybe 2g carb; lunch was a mixed green salad with radishes, tomatoes and chicken, with mayonnaise, about 10g carb; a total of 12g of carb so far.
That means I've got at least 8g of carbohydrate left for supper, to a maximum of 58g, but it's not a treat day today so I shan't go up to 70g for the day. In my freezer I have a chicken ready meal from one of the biggest supermarket chains, which has 7.6g of carb per half pack. It's quite high fat by some people's standard (15.4g fat per half-pack), but I don't control my fat intake, so it's fine for me.
If I'm greedy and eat the whole pack, with maybe another small salad or some broccoli and cauliflower, that's about another 20g of carb. So if I add together 2 + 12 + 20, that's 34g of carb for the whole day. If I add on a very few nuts or maybe a very little black chocolate or perhaps one glass of wine, I can still come in at around 40g carbohydrate for the day.
And I haven't been hungry at all!
Read the labels, pick good food not the cheapest option, and remember a meal doesn't have to have bread, pasta, rice or potatoes - or, for that matter, a pudding! If you need something to 'finish' the meal, have a bit of cheese but no biscuits. Or have crackers/biscuits - eg a couple of plain oatcakes at about 5g carb per oatcake. NOT sweet biscuits! Butter is fine - carb-free!
Next time you are able to have a leisurely supermarket shop, take some time to read the labels and stock up the freezer. Make sure they don't need to be defrosted before cooking. I tend to stick to about 5g of carb per 100g, and control my portions. I never pick anything with rice or potatoes or pasta included. If you want a curry, serve it with cauliflower instead of rice - very good!
Enjoy your shopping
Viv