Does taking BCAA's burn fat instead of muscle when doing intermittent fasting?

Exert judgement when you read and watch and listen.

Because physics, "weight loss aids" is woo.

A consistent calorie deficit is what creates weight loss.

When you lose weight, you lose some fat and some muscle. Unless you eat way too little, most of what you lose is fat.

Intermittent fasting is a range of ways to time your food intake. Meal schedule has nothing directly to do with calorie deficit, but indirectly - because it can have an impact on satiety and general feeling of wellbeing - in how easy it is to stick to. Hunger is normal, and good, as long as you're properly fed. Starving yourself is not good.