Marinade with or with out sugar?
Yes, the sugar will temporarily draw some moisture from the meat.  However, that sugar/water solution will also gradually diffuse into the meat, and the sugar will end up pulling in more water in the long-term.

In any case, the effect is usually small, and any (probably temporary) moisture loss will only be from the outermost 1/8" or so of meat, which will likely dry out in the cooking process anyway.  (To see how the marinade mostly works on only the outermost layer of meat, see some of the photographs at this link.)  The interior of the meat will likely not lose any moisture at all, particularly in a wet marinade.

Over many hours or days, small molecules like salt and sugar in a marinade will be able to penetrate beyond the surface layer and flavor the meat, but the process of moving beyond the surface is quite slow.

Mostly, one includes sugar in a marinade to thoroughly coat the surface of the meat with sugar, which will aid in browning reactions that enhance the flavor of cooked meat.  Too much sugar can cause the surface to brown excessively or char, but a little will significantly enhance the flavor of the outer layer.