I clean the windows of quite a few restaurant and cafes as I'm a window cleaner. I don't charge money but instead do the work for free food. It means I never have to cook or buy food. They're happy and I'm happy. It's almost like a bartering way of life but I never take the piss. I often do extras like clean the shop signage etc, degrease the pavement outside, and so on.
I have found that by being like that and building up a relationship with those who work in these places that when I call by to collect payment, in food of course, I always am reasonable and nearly all times I get extra thrown in. Tonight at one Indian takeaway I simply asked for Bombay Potatoes and the owner said is that it? I said yes. I got Bombay Potatoes, Onion Bajees, Cauliflower Pakoras and 2 chapatis. What a meal and I have left overs for tomorrow. Tomorrow though I'll be collecting two falafel wraps from another shop which means food for Sunday and Monday as well. then on Tuesday I'll be collecting payment from a burger place, which has won national awards, for a veggie burger and I know they'll add in extra's but I always ask for the basic burger and genuinely, I don't expect the extra as that was not part of the original agreement.
Burger Bros. If you're ever in Brighton, UK, the food is all 100% organic and amazing whether beef or veggie.
https://www.burgerbrothersbrighton.co.uk
My point is though, treat staff properly, be polite and friendly, and you'll get much more than if you have a sense of entitlement.