To make instant hot ice or sodium acetate, first pour two jugs of vinegar minus one cup into a large pot. Then, slowly add baking soda to the mixture and stir it. When the vinegar and baking soda no longer react, stop adding baking soda. Next, add the rest of the vinegar to the pot. Boil half of the solution off and cool it down to room temperature. For better filtering, add charcoal to the mixture. Filter out the charcoal with a wire sifter. Heat up the solution again and filter it through coffee filters. Boil the solution until half of it has evaporated. Cool two tablespoons of the mixture to room temperature. You will now have sodium acetate crystals. Cool the rest of the liquid to room temperature. Drop the sodium acetate crystals into the mixture to finish making the hot ice.