"Others have mentioned complaints about breakfast being crowded or not well-stocked. That was NOT my experience. Plenty of food was available at all times during the morning hours. There were three rooms for seating in addition to the "lobby" by the bar, three coffee machines, and two juice machines, plus milk and tea areas. Gluten-free rolls were available every time I asked.
The Diegem train station (and Diegem bus stop) is an easy walk but part of the distance is not well-lit at night. The Diegem KENNEDY bus station is right in front of the hotel. Take 3 euro bus from airport.
If traveling by train or bus, you may want to enter by the Greenhouse office entrance or the ParkingHouse sidewalk. It's just a 3-4 minute walk through the parking areas from Diegem KENNEDY to the hotel entrance. (I suggest the STIB/MIVB app for purchasing tickets and tracking transportation options, though the latter is also possible with Google Maps.)
Be sure to choose Holliday Inn EXPRESS if using the Uber or Bolt App, or you'll end up at the other Holiday Inn a kilometer away.
There are items for sale in the hotel snack show (water, non-alcoholic and alcoholic beverages, chips/chocolate, even sandwiches/salami bites). They are more expensive than a grocery store, but the nearest is beyond the train station (1+ km away). Fruit-infused water is free in the lobby during waking hours.
The hotel restaurant/cafe has limited lunch / dinner items but what I ordered (seafood stew?) was delicious. "