I try and save money on hotels by booking online in advance to secure rate, then check on the day before I travel there to see if any last minute deals are on, and if they are I cancel my booking (used with a pay as you go card with no money on in an alias name) and rebook.
Food, when staying in hotels take a good sized handbag down to breakfast and fill it up, bottles of water, fruit etc.
I also take every tea bag, sugar, milk, bathroom consumables from every hotel each day so staff replenish each day and I have a stash of them for clients or myself.
I have a few empty bottles of water which I fill up with tap water and put in the fridge, no ones ever noticed. And I buy cheap mouthwash but fill up Listerine bottles for clients.
I have also swapped work clothes dresses,bedroom shoes etc and uniforms but never knickers lol.