Besides real-estate, what are ways one could flip, lets say $10,000, a few times, in 3 months?
1) USD dominates everywhere outside of Europe. Still dominates in China, at least for now, just to clear that up.
With that being said, most places in Latin America have interest rates as high as 18-24%, in Southeast Asia as high as 60%. It's a bit risker, but you could do chattel lending (e.g. pawn shops, cars, etc), at 20-30% of fire sale value, and cake off the interest. You can buy portable technology (e.g. used cell phones/laptops/etc), and flip them in said countries for 50-100% more than you paid for them as well. But then you got to deal with the transport, customs, import regulations, etc etc, and then make sure you don't get robbed once you get there.