My dad told me stories of him chucking a bag of sugar into mixers when pouring slabs if the first truck was taking too long and the next truck got going too early. So a fully loaded mixer is going to need more than one bag to fuck up the whole batch. Fortunately there’s a nice cone at the top which makes it easier to chuck stuff into the mixer, I’m sure you and maybe 5 of your close friends could take one or two bags each.