For the best root beer floats, you want to start with frosted root beer to get a delicious slush consistency.
For the best ever root beer floats, freeze the root beer in a plastic bucket with a lid on until it's frozen to a slush consistency. This takes about 2 1/2 hours or more depending on your freezer.
Chill the mugs: Fill the mugs with ice then add cold water filling it almost to the top. Put the mugs in the freezer for 5-7 minutes. When the mugs are frosted, just empty them and keep them in the freezer until ready to use.
When ready scoop vanilla ice cream into each frosted mug. Gently pour the slushy root beer into each one. Top with a dollop of cool whip or whipped cream and a cherry on top. Enjoy!