I bought these watermelon flavored ices from the supermarket because they have 100 calories per cup and 0g of fat and saturated fat. But they do have 24g of sugar.
Will eating these be against my weight loss intentions?
It sounds like nothing but sugar to me. Most highly processed foods work against fat loss, and this sugar shot is no different. At the very least, it is empty calories--calories that perform no function.
The thing to be concerned with is what other affects those empty calories can have on your body. It might be just enough to kick start your metabolism, and cause your brain to signal the "I'm hungry, feed me" response. If that happens, the net effect is it incites you to overeat.
In general, any calorie not doing anything for you while you are attempting to lose fat will at the very least slow your progress down. It's easy to justify little cheats, and tell yourself that "it's not that bad". Until you bring yourself into discipline, you should not give yourself little treats. You should be finding out how to make the food you should be eating more tasty.
You may think that this drink is only 100 calories. And that may be so. But, what it doesn't tell you is that the significant sugar (24g) will spike your blood sugar causing your body to produce more insulin. When your body produces insulin, it immediately goes into fat storage mode. So instead of burning some fat (in addition to carbohydrates), it burns 0 fat and continues to store energy reserves as fat.
A rule of thumb that I use (works for me, may not for you), is if sugar is listed as the first or second ingredient and/or is more than 8g, I don't eat or drink it. This includes 0-calorie "sugars" like aspartame.
Keep your blood sugar in check, and you won't need to be on a "diet".