That claim doesn’t hold up. No drink can make you meaningfully “slimmer” overnight in terms of actual fat loss.
What can happen is temporary changes—like losing a bit of water weight or feeling less bloated—especially if the drink affects hydration or digestion. But real fat loss comes from consistent habits over time: calorie balance, regular movement, good sleep, and sustainable eating patterns.
If you want, tell me what’s in the mixture you saw, and I can break down what it actually does (and whether it’s useful or just hype).