bitcoin, you may get 10x in six months
Bitcoin is virtual currency based on massive electricity consumption. Due to the ever increasing difficulty of mining, it is effectively a Ponzi Scheme.
But if it continues the way it has been, then it can accomplish the goal.
The worry is that when the crash comes, no one will be willing to buy. Or even if you find buyers, what if everyone starts withdrawing their money from the exchange, and the exchange doesn't actually have that liquidity...
The volume is not great. You'll lose quite a bit on exchanges. It's probably the same for stocks or real estate, but something like gold is much more liquid for a million dollars. Or gambling.
However I have heard of a few exchanges that will let you cash out 1m+ in BTC.