In general, a minor doesn't make a degree more attractive to employers, but some majors benefit from a carefully selected minor. If the subjects of your major and minor are unrelated, spending the extra time and money on courses isn't likely to make a difference.
Dry ice, of course, is frozen carbon dioxide — about 107 below zero. It also would create a potentially toxic layer of carbon dioxide at the surface level, and will throw your pool's acidity readings way out of whack. As for the cooling effect, not very much.
While most commonly used in drag racing, a spool differential can easily be used in drifting, acting the same as a welded differential. A spool's purpose is to remove the spider gears from your differential entirely, instead replacing them with one solid piece.
Milk. Traditionally hot chocolate is a bedtime drink too, but it doesn't work as well as milk. Chocolate milk contains high levels of xanthines, the mother of stimulants like caffeine.