We knows that the crypto currency investment can give us lot of profits even in short time but this is very new there are lot of invesments like real estate,gold,mutual funds silent partner in businesses and lot more but what you think which has highest ROI in short term other than crypto invesments.
My opinion is that real estate can be that one,since my grandfather used to be like buying and selling the lands and made tons of money in his life time but I didn't do that such kind of traditional invetment.
Another one is stock market if you picked the right one you can make a huge profit, it's like investing in Cryptocurrency, some stocks can go as high as 50%, another form of investment is food business, just look for a good location and create a unique and mouth savoring food and you are on your way to profit.