The obvious idea how to exploit them is to invest something small at the first day, withdraw it as fast as possible and repeat just with the interests from the previous bet (and of course take some money away from every successful round).
Has anyone tried that? Have you been successful? Is this kind of gambling popular/common. Has it name?
Most of them will exit scam before you reach any profit. It is not possible to have a strategy. Unless you have an HYIP monitoring site and can get lots of referrals you will not make any profit in the long run. It is purely gambling. If you were lucky enough to make a lot of money in your first investment you should immediately get out and never invest in a similar program again.