There are some really great apps available that give you rebates when you purchase certain grocery items. I am going to take a minute and tell a little bit about each. I currently use all 3 and like each one for different reasons. Sometimes something you buy (ex.-gallon of milk) may be used on more than one of the apps.
Ibotta
Though it requires a little more work than the other two,you have to scan the product as well as take a picture of the receipt, it is still one of my favorites for several reasons. First off it's super quick once I submit a product that I have purchased I usually have the money in my account within 6-12 hours. Second, on this app you may cash out as soon as you reach a minimum of $5 (the other two you have to be at $20). Also you can request your rebate in different ways such as a transfer to your paypal account or an iTunes gift card. One other thing that I should mention about this app is that it is divided up into store categories and certain items must be purchased a certain stores...not all stores are available.
Checkout 51
This app is also super fast, however not quite as fast as Ibotta but money is usually credited to your account in 12-24 hours. You only have to take a picture of your receipt and don't have to worry about scanning the product. Another thing I like about this one is most of the items don't have stipulations on where you have to buy them so you can shop anywhere you want. They also change items every Wednesday so you always know that is the day to look for new deals and that you have week to redeem them. I love this app because there are usually options for things like bananas, apples, carrots, yogurt, etc (any brand) which I normally buy anyways. Once you have earned $20 you can request a check.
Snap
Is the newest grocery rebate app it is produced by Groupon. For this app you can shop anywhere and only have to take a picture of your receipt. You have to earn $20 before you can request a check just like Checkout 51. The good thing about this app is that they seem to bee higher value rebates. Some examples $1 on any milk, $1 on any bread, $1 on any bag of candy. Right now the Huggies deals on this App are awesome especially if you pair them with coupons, because you can get $3 for buying diapers and $2 for buying wipees-most packages of wipes are around $2 to start so it's pretty much like getting them for free. One thing to note about this app is that there are a certain number of rebates available for the different items. When they run out it will let you know that they are no longer available. Usually you can only claim one rebate per item, but sometimes they will offer unlimited or 2 rebates for certain items. This app tends to take a little bit longer to verify your purchase than the other 2 sometimes between 24-48 hours, but it could be cause they are newer and hopefully that will change over time.
If you haven't already I would recommend downloading all three of these apps. Play around with them, use them, see which one fits with what you are doing. Maybe chose to use just one or chose to use all three, but definitely use them as they can be a great tool in earning money on the things you purchase.