There's no single "best" weight loss powder that comes in a sachet. Different sachets contain different ingredients and work in various ways. It's important to consider your individual needs and consult a doctor before choosing one.

Weight loss powders that come in sachets are dietary supplements that come with various ingredients. They are marketed to support weight loss along with diet and exercise.  

The effectiveness of weight loss sachets vary depending on the ingredients. 

The best weight loss sachets for you might depend on your particular need and the ingredients in the products. Hydroxycut Hardcore Ultra Shred Drink Sticks for example have green coffee bean extract to support weight loss along with diet and exercise.It also has Paraxanthine, a caffeine metabolite. Hydroxycut Weight Loss +Electrolytes is a weight loss supplement that also contains caffeine for energy. It is a zero-calorie and zero-sugar energy-boosting drink.

Focus on ingredients backed by scientific research. Avoid powders with unrealistic claims. Consulting a doctor or registered dietitian can help you choose a safe and effective option.

Dosage and frequency depend on the specific supplement. Always follow the manufacturer's instructions. Do not exceed the serving size mentioned on the packaging. Consult your doctor to determine a safe and appropriate usage for you.

Long-term weight management relies on sustainable lifestyle changes like healthy eating and regular exercise. No supplement will offer a magic solution. 

Mixing your sachet with water is usually fine. You can explore options like fun mocktails  or adding fruits for extra nutrients.

In terms of timing, make sure you follow the directions on the label. For example Hydroxycut products should be taken twice daily, 30-60 minutes before your two largest meals.