The best cheeseburger in Berlin costs less than 5. Burgermeister is mandatory in town when you're craving for a basic and delicious to the bits chesseburger. 

Cosmoveda is a hidden xberg gem. It's an Ayurvedic supermaket that happens to come with a kitchen with it. There you can find a delicious Ayurvedic lunch menu (with soup, main and a little dessert) in 3 different sizes, prices starting at just 5,90. Not to mention you can shop the ingredients that you just ate in case you want to try to cook Ayurvedic yourself.  

A very nice little second-hand bookstore, including a shelve with international books in French, English, and Spanish too. Always nice people to meet and a great selection of art and cook books, for affordable prices.

Soluna bakery is where I get my (delicious) bread.

It's an indoor market, which makes it a great option in winter if you are looking for anything from kitsch to classy. I like it because you find lots of old objects that transport you to the past.