Combine sugar, butter, water and cinnamon in a large heavy pot (at least 5-1/2 quart). Bring to boiling over medium heat, stirring constantly; continue to cook until the sugar is dissolved and the mixture becomes syrupy, 4 to 5 minutes. Remove pot from heat.
Add the popcorn, cereal, cashews and raisins to the pot; stir quickly to coat all ingredients evenly with the sugar mixture. Turn coated popcorn out in single layer onto 1 or 2 large baking sheets lined with waxed paper or parchment paper. Break up any lumps with your hands. Let popcorn mixture cool for about 10 minutes. Makes 12 cups snack mix.
