Please choose the correct solution to the question: How can I have ice cold water in my water bottle from home?

Solution1: Fill bottle 1/3 way with water, lay on it's side freeze, then fill with cool water when you leave the house.

Solution2: Fill bottle 1/3 way with buttermilk, lay on it's side freeze, then fill with cool water when you leave the house.

Answer format: solution1/solution2
Answer: solution1