Shopping & Food

Free Tap Water in Belgium | A great initiative that promotes free tap water in Belgian restaurants. They have made an app where you can find all of the restaurants in Belgium that currently offer free tap water. You can download their app for iPhone users here and for Android users here.
Too Good to Go | Every year, 1/3 of all the food produced is thrown away worldwide. Thanks to Too Good To Go, millions of meals have already been saved. With this app, you can enjoy good food at a very big discount. It's a great app and I use it regularly. I pay 3 Euros for meals that have a value of 12 Euros or more.
Social Deals | An app where you can get discount on meals and much more
myShopi | This a a good app for people looking to save on their groceries. myShopi collates all the on-going promos of major grocery stores in Belgium. You can apply for rebates & cashbacks within the app, making it very easy to use. I was able to get some stuff for free with their cashback function.
Deliveroo | Order meals from the best restaurants in your area and have them delivered to your home.
Uber Eats | Exactly the same idea as Deliveroo. I use both because there are some restaurants that can only be found in one app and not the other.
KBC Mobile | It's a good idea to have an app for your bank easily accesible on your phone. The bank I recommend in Belgium is KBC (or CBC in Wallonie). They are foreigner-friendly (I was able to create a current account with just my Arrival Statement, 3 days after I arrived in Belgium). Their app is also very handy because, unlike most other Belgian banks, I do not need to use a bank card reader to make online purchases at home. You can also buy cheaper train tickets and De Lijn bus & tram tickets with the app.
Vinted | Buy and sell clothes, shoes, etc.
2dehands| Buy and sell second hand items

Job Hunting

Babysits | An app for babysitters and parents to connect.
Indeed| A good online platform for finding English speaking jobs in Belgium.
NOWJOBS| This app is perfect if you want to find part-time/one-time jobs in your area.

Read my guide to finding a job in Belgium here

Language

Duolingo | A fun and effective way to learn basic Dutch & French (and many other languages).
Google Translate| This app is absolutely indispensable to surviving here in België and in any strange land. This app can even translate text on photos, which is very handy.

Getting around

Railer| This minimalistic iOS app has been voted as one of the best apps in Belgium. It is the best iPhone app for getting around on the Belgian railways.
SNCB National | If you don't have an iPhone, then you'll just have to make do with the SNCB app. Its only advantage is that you can buy tickets within the app. I don't buy tickets that often because I usually buy a Go Pass 10 at the station (you can travel within all of Belgium at €5.20 per way if you are under 26 years old).
Google Maps | I use this app for checking bus & tram routes, biking & walking routes, and discovering new restaurants/shops.
Cambio | A car sharing app. Obtaining a Cambio card gives you access to their fleet of cars. You can use it for as long as you want: for one hour, a few hours, a day or longer. Cambio is perferct for long trips. Things to note: you can only drop off the car where you picked it up AND an annual subscription is required.

Poppy | This app is only available for use within Antwerp, so it is perfect for quick trips (big grocery store & Ikea hauls). You can can drop off a Poppy car in any part of the city (but you can still drive to anywhere as long as your last destination is the city of Antwerp).
Waze | Using Waze can save you a lot of time because it shows you driving routes with the least traffic.
Buienalarm| Not exactly an app for getting around, but I always check this app before going out. It is the most accurate in predicting precipitation in this very rainy country. Do note that it only shows the intensity of the potential rain over the course of the following 2 hours.
Bike sharing apps | There are well-established bike-sharing schemes in the cities of Brussels (Villo!), Antwerp (Velo), and Namur (Libia Velo). Blue-bike, on the other hand, is Belgium’s nationwide bike sharing system. Check out this site for comparisons of the 4 options.