For hot-water bottles, use heat-resistant plastic bottles, hot water under 80 degrees Celsius, and most importantly, odor-free socks! [From "How to Craft Safety"]
Materials and equipment: PET bottle for hot drinks, socks, warm water (70-80 degrees Celsius)
How to craft:
1. Place bottle on steady surface and carefully pour in hot water.
2. Cover the bottle with two layers of socks.
Memo: Please ensure to use PET bottles made for hot drinks only.