Trying to do things on my list...

So I'm a bit short on cash these days, a combination of getting almost no hours this week, being sick for most of the week two weeks ago and getting a new tattoo on Saturday, so I can't do very many of the things on my bucket list because a lot of them require dinero. So I am trying to work on some free or cheap things on my list.

One of the cheaper things on the list is "pay for the person behind me." I don't have a car so I can't do it in the drive through and we don't have toll booths. I was thinking of trying to do it at McDonalds or some place but I don't know how I would know what their food was going to cost when they haven't even ordered it yet. Ideas?