Can I split a USB cable's male end, add a second male plug, and draw 10V from 2 ports instead of 5V from one port for a single device?
No you cannot!
Both USB sockets are probably even the same power supply so the 5V of both USB ports is connected to eachother and the 0V/GND is also shared. 

If you had two different adapters with internal galvanic isolation (transformer) it would be possible to make 10V 1A of two 5V 1A USB ports.