Bitters and gin
jenever or genever, the predecessor of english gin. it's available in two types, called oude old and jonge young, which have nothing to do with aging, just the distillation style. the more traditional "old-fashioned" oude is sweeter and yellowish in color, while jonge is clearer, drier and more akin to english gin.
beerenburg, is an alcoholic drink, made by adding herbs to jenever. it has an alcohol percentage of around 30%. the original beerenburg was made halfway through the 19th century with a secret mixture of spices of the amsterdam spice merchant hendrik beerenburg, to whom it owes its name. despite it being "invented" in amsterdam, it is considered typically frysian.
Although the Dutch beer "Heineken" is one of the world's most famous beers, it is just one of the many beer brands in the Netherlands, and many Dutchmen consider it to be only a second-rate pilsener. You can get all kinds of beers from white beer to dark beer. Popular brands are Heineken, Grolsch, Brand, Bavaria, Amstel etc. There's a certain regional variety in the beers you'll find; whereas, in the Western-Netherlands, many pubs serve Heineken or Amstel, pubs in Brabant will generally serve Bavaria or Dommelsch, in Limburg Brand and in Gelderland Grolsch.
In addition to the usual lagers, try Dutch white beers witbier, which are flavored with a spice mix called gruit and thus taste different from the better-known German varieties. Fruit-flavored varieties are also available.
Traditional beers come from monasteries in the South of the Netherlands Brabant and Limburg or Belgium. You can visit a traditional beer brewer in for instance Berkel-Enschot just east of Tilburg at the 'Trappistenklooster'. It needs to be said that the brewery is now owned by the big brewer Bavaria, so it's not so traditional any more.
There are also a lot of excellent small and micro breweries Brouwerij 't IJ, Brouwerij de Molen, Brouwerij de Prael etc., if you're a beer lover in Amsterdam consider visiting the beer shop "De Bierkoning" near "De Dam" central square of Amsterdam, it has over a thousand beers, about half of it is Dutch and "Brouwerij 't IJ".
Most breweries nowadays also produce a non-alcoholic variant of their beers, like Bavaria Malt or Amstel Malt. Which consist sometimes 0% or less than 0,5 alcohol and is very suitable for people who would like to drive and don't drink or sometimes called "de Bob" as promoted in its campaign.
Hot chocolate with whipped cream is a winter tradition in the Netherlands. It really fills you after a cold walk. In the summer you can also get it in every decent bar, however sometimes it's made from powder as opposed to the traditional kind regular chocolate melted and mixed with hot milk, and doesn't taste that good.
tea and coffee
Dutch drink black tea, and it comes in many different tastes, from traditional to fruit infusions etc. Luckily, if you're English, you get the teabag served with a cup of hot but never boiling water, so you can make your own version. Milk in your tea is almost unheard of and given only to children.
Coffee is almost compulsory when you are going to visit people. One of the first questions when coming through the door is often "Koffie?" and it is served in small cups a half mug with cookies.
If you're from the States or Canada, you can drink one cup of Dutch coffee in the morning and add water the rest of the day! If you order 'koffie verkeerd' which means "coffee the wrong way 'round" you get a cup of more or less half milk and half coffee, more like the French 'cafÃ© au lait' or the Italian 'caffe latte'.