None - the transmission in almost all bikes (my BMW airhead is a separate unit taking gear-oil) is in the crankcase with the crank, clutch etc. It's lubricated with the engine oil.
You'll hear some people mention the use of ATF in their forks, but that's about the only time anyone will mention transmission fluid.
Perhaps the CB750A (automatic) has different lubrication, but even it I'd guess just uses the engine oil for protection.