Aunt May giving Peter lunch money, but Peter being the sweet boy that he is simply skipping lunch every so often and then taking the money and sneaking it into the dirty laundry so that when May is doing it she ends up finding it back. Every time she gives a sigh of relief and needs a moment. She's got no idea Peter's doing this.
Okay no you don’t understand this happens all the time. It also doesn’t stop at lunch money, Peter works two jobs, one as a freelance photographer during the school year and another as a waiter during the summer. He puts aside a small bit of cash for himself to use as spending money but the rest of it he sneakily deposits into May’s bank account. He’ll buy lunch with his own leisure money and sneak the cash May gave him into dirty laundry, he’ll save up for a month just to go to the movies but he’ll give that money to May in a heart beat if he hears how tight things are that month.
But on the flipside. People do that to him as well. Harry Osborn often will pickpocket his wallet and slip 5 dollars into it because he’s worried about his friend.