To double it safely i will build a food business which most people really like. I'll build a restaurant spending all $100k. Although doubling it will require some time but it will be safe in that way. Rather than investing it on some networking or use it as trading capital which have a high risk of doubling money.
I think business is still at risk. many restaurants in my town went bankrupt because they could not compete with competitors, yeah it is the risk of a business,
there is always a risk, if you do not want to see the risk. Do not grow your money