my dad showed me if you toss it up in the air and let it fall most the water will come out. at the tire shop i learned another way that was easier. you stand the tire up.
then you stand facing the sidewall reach over to the other side grab the tire bead on the top.
then lean the tire in the top part of your knees and lean back with a fast steady motion.
if you do it right you will lift the tire off the ground and the tread of the tire will now be slightly higher than the rest of the tire and stop lifting it for a second and hold it in place.
this has to do with newton's law of motion. the water that was sitting on the bottom will still rise after you stop moving the tire. the water will ride up the tire and ride tire wall. the water will continue to ride the tire wall till it hits the bead where it will simple fall out of the center in a water fall. just dont wear good shoes and keep your feet spread.
i know i dont write too well so it maybe confusing, i may have to make a video lol