I know it isn't an investment, but in the last few years some "high risk" investment funds have appeared, and in them you can either lose it all or earn a lot of money.
Isn't this basically the same as gambling? Wouldn't it be faster to just deposit the amount in a casino? At least you'd be able to spend your earnings much sooner

Actually gambling is a game of 99% risk of money loss garranty . So here is not a matter to consider gambling as a high risk investment . And in investment we have the history of the investment foundation wether he is paying or not but in gambling everything is for loss .
Even though gambling has 99% chance for losing your money, there is still 1 % chance you could be rich from gambling, and there are few lucky apeople who successfully reach that. Gambling will considered a "high risk investment" if we invested our money and set to max kelly in a gambling site (IMO)
I think we should not put our money in risk only for 1% of winning chance, we should only play gambling up to the limit we can afford to lose, actually we should erase the possibility of making huge amount of money from gambling because it is not so easy to make money from gambling.