Wikihow says you can do it in a shaker-cup with a lid on top ... than I tried a recipe for avocado but since I can't make the avocado so smooth without a mixer I got green colored small bits from crushing it with a fork floating in my chocolate-colored drink
It tastes great but I would say next time I should use a banana if I ever buy one instead of an avocado
And from how it looks like I am now pretending I made bouble-tea instead