The situation cannot be analyzed w/o alcohol. Combining alcohol is too much. Coke gives you sort of a 'mental buff' where it gives you your mental control back but your body still has the same amount of alcohol in it.

This allows you to do more of the alcohol, even past where you would have normally stopped and this is OK up to a point, but if the coke wears off you get re-drunk far past you could have gone. It hits you like a brick wall. Shit goes bad fast.

Coke has a much shorter duration than either alcohol or heroin. Timing is key and can get complicated. Either 2 combinations of the three are already dangerous enough.Adding the other is too much.