Me too, I try to be organised with what tins I buy, only buying stuff I know I'll use. Tuna in the 4 pack, is great as it takes up little space and I'll always use it.
Can you get yourself on the allotment waiting list, or even better an allotment? Most places do have a waitlist, but it's great to have some outside space.
I haven't got space for lots of water, so just make sure there's some in the kettle, and I refill my drinking water bottle each time it's empty. Some is better than none.