Being told I can't drink water at my desk!

my husband is a nurse and they made a rule where the nurses cannot have drinks at the nurses stations (where else would they sit it? on top of a patient?)...so one of the ladies he works with bought a bunch of those drink holders that have the lip that slides into the car door, and they put that lip thingy into the side of their scrub pants, so they walk around with these drink holders on their scrubs. its pretty funny looking.
just had to throw that out there.
and i would fight my employer on that. i mean really...do they want people to be healthy or not? 
you could call into work and tell them you are dehydrated from not getting all your fluids since you can't drink at work.
(im a smarty pants i guess)

First, get documentation from your doctor that says due to your surgery you have to drink more fluids and more frequently.  Then take it to your HR department.  Mention the word "accommodate."  You will have a documented medical condition and should be covered under ADA to some extent.  They will have to make accommodations to your condition.  My workplace had to "accommodate" me due to my odorous emanations!

It never fails to amaze me the anal attitude of people in charge. You can be darn sure if that person had WLS they would have water at their desk. Maybe as a group, your co-workers can help and all of you push back. If not I don't think the company has any solid ground to stand on and a good lawyer and judge would shame them.

Tell them it's no****er, it's vodka. (*grin*)

***UPDATE***
So I gathered all your wonderful advice and did the following:
* Contacted my surgeon's office for a note stating the medical necessity of being hydrated as a post-surgical patient.� They were really surprised and annoyed about it and they are contacting the person who is doing the enforcing, as well as sending me a note on their letterhead, to do with as I see fit.� If the BS continues I will go to Employee Relations with the letter and any research I can dig up from the ADA.
* Purchased a spill-proof bottle and will be demonstrating it to said person, and also keeping it with me at all times. Also I will ask on behalf of my co-workers if these bottles could be purchased in bulk and used by the staff.

Thank you all for your responses and suggestions!� As you can see I am putting them to good use!