There must be a desire to even bring a glass of water to drink. Without desire, no movement is possible. First, there is a sensation of thirst; out of that thirst, there is the desire for drinking water.
So, when desire is the fuel to carry out normal daily activities, what does it mean that Buddha didn't have desires?
My guess is When there was a sensation of thirst, Buddha used to not identify himself with the sensation. In other words, there was an absence ego-identity with the thirst. But again, the desire to drink water, eat, move, etc. was arising. From where it was arising?
Generalizing it better, the question turns up, Can there be an action free from the taint of desire? Because desires seem to be driving force of any action. Doesn't it? If there can be, what is the nature of that action?