Go here
http://evreward.com/store/go/1713 and choose the program you want. There is also a selection of hotel point options. Purchase a banana for 30 cents and opt for store pick up as there is no minimum order nor handling fee for store pick up.
I can't confirm this actually works as I just placed my order so I expect it will be a few weeks before the miles post...if they do. I ended up finding a few really good bargains and ended up spending about $20. Also, this program may not be available where you live. I live in an urban area and the closest participating store to me is about 6 miles away.
While you could do this offer for 30 cents (maybe someone will find something even cheaper?), I think you may want to make a purchase for at least $1 as some programs round anything under $1 to zero for mileage qualification. Just a thought.
Safeway also has a similar program
http://evreward.com/store/go/1911 that lets you about the same number of earn miles/points but you must place a minimum order of at least $50 to be delivered. First time delivery is free with code EASY7. While not as big of a bargain as getting the miles for the price of a banana, we are talking about groceries which you would need to buy anyway.