What happen if you mix Xanax (alprazolam) oxycodone seriquil and cocaine at same time?

Mixing. Very unwise! why use stimulant with sedatives? Why risk deadly overlap of side effects, such as respiratory suppression and death! too many celebrities and wannabes party with alcohol, benzodiazepines, and narcotic pains, and die in a bathtub, or while sleeping. Get some professional help for your desire to overlap these dangerous drugs, before you have a fatal accident!
Not cool. . Drug abuse can have serious and lethal consequences. Seek help and only take medications as prescribed.
Mix drugs. No doctor with any good sense will prescribe that combo. You are trying to feed your addiction? Please do not do so! all those are addictive drugs and combined addiction will unvoidably destroy life.
Speedball. If you do that you will be giving yourself the equivalent of a "speedball" -- which can be deadly. Some people do things like this thinking they can control the outcome -- and die of heart arrhythmias, strokes, or drowning in bathtubs as my colleagues said. Sounds like you need serious help, and i hope you decide to get some before your addictive behavior kills you.