If you don't have a bottle brush to clean the inside of the bottle that can be heated up to 80 degrees Celsius, you can use the following method to clean the bottle. Here are the steps: **Materials Needed:** - Warm water (maximum 80 degrees Celsius) - Dishwashing liquid - Rice (uncooked grains) - Optionally, baking soda and vinegar for stubborn stains or odours - Long wooden spoon or a long piece of kitchenware **Steps:** 1. **Empty the bottle:** Ensure the bottle is completely empty and remove any leftover liquids. **Rinse the bottle:** Rinse the bottle thoroughly with warm water up to 80 degrees Celsius to remove loose residue. **Make a soapy solution:** Fill the bottle with warm water and add a few drops of dishwashing liquid. Screw the lid on tightly and shake the bottle well to distribute the soap. **Add rice:** Pour a handful of uncooked rice grains into the bottle. The rice acts as an abrasive and helps remove deposits and stains from the inside of the bottle. **Shake the bottle:** Seal the bottle tightly with the lid and shake it vigorously for a few minutes. The rice grains will scrub the inside of the bottle and loosen any stains. **Rinse thoroughly:** Rinse the bottle thoroughly with warm water to remove all soap residues and rice grains. **Optional: Use baking soda and vinegar:** If there are still stains or odours in the bottle, you can make a solution of baking soda and vinegar as described earlier and let it soak in the bottle before rinsing it again. **Allow to dry thoroughly:** Allow the bottle to dry completely before using it again. This method should help clean the inside of the bottle, even without a bottle brush. Always follow the manufacturer's instructions and do not use water hotter than the recommended temperature for the bottle.