If you were using something made of glass or something like that, you could just kinda scape the substance once it cools down and is no longer a runny liquid. 

Off the top of my head i can think of heating the foil lightly, so the drug becomes runny (but it's not vaporising yet), and you can kind of try to position the foil so it drips into some sort of container i guess youre using, or something. But idk really, i have never done that. OR you can try to straighten the foil, like, make it as flat as you can, heat it up a little, then scrape the drug out with something.


And first and foremost, please don't smoke from aluminium foil - when heated, it releases some nasty shit  
https://en.wikipedia.org/wiki/Argyria