Pour the rum and fruit juice into a blender, on top of 6 - 8 ice cubes. Blend the mixture until it is smooth. Then pour the contents into a 16 ounce glass or beer mug and pour peach soda into the glass until full. If you can't get peach-flavored soda then orange or another fruit-flavored soda will do in a pinch. Toss in a straw and enjoy!