Power-up Jars are boosters you can get before entering a level. They have different features that can boost your performance in a level. You can only use one of each in a level. Their appearance on a level start pop-up varies according to the level's needs. For instance, if you are playing a timed level, Extra Time Jar appears in the pop-up. 

You can buy them with Coins by opening a level start pop-up and clicking on the Power-up Jar you want to purchase. Once you purchase the Power-Up Jar you wanted, make sure to click on the Power-Up Jar to use it in the level. It'll have a small tick on the corner when it's selected.

Anti-Burn Jar prevents the cooked dish from burning when you use it in a level. (9000 Coins to buy 3 Jar)

More Patience Jar increases the duration of costumers by increasing their patience. (9000 Coins to buy 3 Jar)

Extra Coin Jar helps you in collecting more Coins per order. (9000 Coins to buy 3 Jar)

Extra Time Jar is used in timed levels and adds more seconds so that you can cook more dishes. (9000 Coins to buy 3 Jar)

Extra Customers Jar helps you by adding more customers to the level when used. (9000 Coins to buy 3 Jar)

Magic Cupcake is the Joker Dish you use when you don't have any time to cook the dishes the customers have ordered. It's placed in the blue shelf you see when you enter a level. You can have only 5 Magic Cupcakes in a level and you can fill your cupcake shelf with using the game Cash (50 Cash to buy 5 Magic Cupcake). You can click on the shelf to take one of the cupcakes and give it to the customers you want to give. They'll take the cupcake instead of their orders any time!