Well the replies in this thread are kinda the same and most are telling you you can't double it SAFELY, double yes safely no I agree with this. Now if you are willing to take risks you could invest after doing research but you would probably want help of a professional as well if it's about this big of a sum
there are actually safe ways of doubling it, you can invest it into bitcoins and then just wait a long time, sooner or later it will happen
But i think at this moment and time is not the bestnidea to store some huge bitcoins and wait for halving miracle its because price wouln't go up so far at this moment sibce bitcoin are continously rotating on different investment structure since people are not waiting for halving and that is far to be happen, and i think there's no best way to double that 100,000 in online venture since mostly of investment site whos existing nowadays are scam.