Like it has already been said, leave a small bowl in with the snake so it can drink if it wants. During brumation a snakes meataboic rate is so slow it probably wont even want a drink.
I must say this.....DO NOT "ROUSE" A BRUMATING SNAKE. Brumation is stressful enough, dont ever do this. Once you put your snake to sleep do not bother them. I cant stress this enough. A successful brumation depends on the snakes lowered metabolic state, when you wake it, all its functions kick back up, and it effectively exits it's state of hibernation.