IF this pipe goes to the toilet, and the toilet is sweating too, you might want to consider a 'mixing valve' for the supply line. By mixing the hot and cold water w/the cold water supply line, obviously, you raise the temperature. And you only need to raise it enough to stop the sweating. As to where you put it, I can't say for sure. It depends on the 'route' the pipe takes to get to the bathroom. Be sure a ball-valve shut-off is installed on the FEED side of the pipe near to the mixing valve. This way, if you need to replace the valve, you can 'kill' the water right there. The shut-off should have a bleeder on it, and it should be installed such that when the water is off, you can open the bleeder and drain the water from the 'uphill' part of the piping.
There isn't any creative solution, cosmetically, to 'fix' this (well, that I know of.) My best to ya and hope this helps.