Hmmm -- Why 1/2 liter bottles of water? Is there a more space efficient size to store 4 liters (~1 gallon)?

For why would you be bugging in? Winter snowstorm? Hurricane? Major flood? Do you expect the power to stay on?

If the office has a real stove, keeping real food may also be something worth considering. For bugging in I always think about not having to resort to MRE's and snack-bars. Is the tap-water drinkable? Would it be drinkable with a water filter?

Is there a couch to catch some Z's?

Also, don't forget all the ingredients for a great cup of coffee and tea. This you should be able to keep in the kitchen.