Try to put it on trading and buy some cheap coins and wait for the price to increase like 200% and sell you shares in that way you can double your bitcoin in a safer way than putting it on different HYIPs out there.
This is most logical and I really think this will give you the most chance. I think bitcoin will be able to hit 1.2k and thats double of the price now. So if you invest 100k it helps bitcoin grow as well and will double your money in a few years.
It is believed that when the SegWit is released to the main chain, the bitcoin price will at least double.