As noted by Wizla, it's per stay. From the t an c's:
- Two complimentary bottles of water per stay at Waldorf Astoria Hotels & Resorts, Conrad® Hotels & Resorts, Hilton Hotels & Resorts, Curio - A Collection by Hilton, DoubleTree by Hilton™, Tapestry Collection by Hilton™, Embassy Suites, and Hilton Garden Inn®.*
* Internet Access and Bottled Water benefits may be included in resort charge, where it applies.
Hilton Honors Terms and Conditions