If the situation calls for IV and the ONLY recourse is coconut water....you have more to worry about than infection. Assuming you have the tubing to administer IV's, you probably have any left over bags (even if empty). Sterilizing H2O and administering is still infection risky...you need to 'refill' the bag-plenty of routes for infection. 20 something years in EMS....don't think I'd ever see a reason to 'use' coconut water. If it gets that bad....there is more to worry about than IV replenishment.