I gave our neighbour some chocs and some wine when they popped in twice a day for our bunnies and when my friend has my budgies at her house I always bring her something edible back. However, when we go away for 11 days in August we're paying for the rabbits to go there and it's costing nigh on £70, but I might get her something relatively cheap; we all like extra thank yous afterall. Plus, I feel that if you get them an extra something (even a box of chocs for £1 or something) they may be inclined to look after the buns extra nicely the next time!