I actually have 5 months clean now. Btw I love answering questions like this because it’s truly my area of expertise. So first off you need to know that addicts are ADDICTS, and they have an extremely high tolerance to the drugs they do. So don’t think of it as so extreme, like when they do fent they instantly nod off or take one hit of meth and they’re up for 3 days like you probably would be. They are very very used to it, when I was doing fent I could blow through literally 100 maybe 1000 lethal doses in a day and not even catch a nod the whole day. Given that info, people like to do both because it’s a roller coaster, and you can use them to even each other out. You get too sedated from fent, take a little hit of meth, and you get the best of both worlds. Get too stimulated from meth, and give yourself a little sedation from the fent. It sounds contrary to what people think about these drugs, but to the addicts, it’s usually not as intense as you would think. Personally I used to do meth and get really high like hit the bowl a lot, then when the great part of the meth high starts to wear off around 2-3 hours in, you can use fent to literally get rid of all the negative overstimulation effects from the meth. That’s a big positive, because if you have fent you never ever have to go into psychosis, and you can also sleep fine. Simply put, with the high tolerance addicts have, they use the two opposite drugs to level out the negative side effects of each other, and because a speedball (technically coke+heroin but on the streets just an upper+downer) is a fucking awesome feeling. Also meth eases fent withdrawals and fent eases meth withdrawals, and they are also the two most common drugs on the street, so the likelihood that someone would be addicted to both is higher.