Thanks to its thousands of lakes, Finland has plenty of water supplies and tap water is always potable. The usual soft drinks and juices are widely available, but look out for a wide array of berry juices (marjamehu), especially in summer, as well as Pommac, an unusual soda made from (according to the label) "mixed fruits", which you'll either love or hate.
Coffee and tea
Finns are the world's heaviest coffee (kahvi) drinkers, averaging 3-4 cups per day. Most Finns drink it strong and black, but sugar and milk for coffee are always available and the more European variants such as espresso and cappuccino are becoming all the more common especially in the bigger cities. Oddly, Starbucks hasn't arrived in Finland yet, but all the biggest towns have had French-style fancy cafés for quite some time and modern competitors are springing up in the mix. For a quick caffeine fix, you can just pop into any convenience store, which will pour you a cuppa for €2 or so. Tea hasn't quite caught on in quite the same way, although finding hot water and a bag of Lipton Yellow Label won't be a problem. For brewed tea, check out some of the finer downtown cafés or tea rooms.
In Finland it is quite common for people of all ages to drink milk (maito) as an accompaniment to food. Another popular option is piimä, or buttermilk. Viili, a type of curd, acts like super-stretchy liquid bubble gum but is similar to plain yogurt in taste. Fermented dairy products help stabilize the digestion system, so if your system is upset, give them a try.
Alcohol is very expensive in Finland compared to most countries (though not to its Nordic neighbours Sweden and Norway), although low-cost Estonia's entry to the EU has forced the government to cut alcohol taxes a little. Still, a single beer will cost you closer to €4-5 in any bar or pub, or €1 and up in a supermarket. While beer and cider are available in any supermarket or convenience store (until 9 PM), the state monopoly Alko is your sole choice for wine or anything stronger. The legal drinking age is 18 for milder drinks, while to buy hard liquor from Alko you need to be 20. ID is usually requested from all young-looking clients. Some restaurants have higher age requirements, up to 30 years, but these are their own policies and are not always followed, especially at more quiet times.
Surprisingly enough, the national drink is not Finlandia Vodka, but its local brand Koskenkorva or Kossu in common speech. However, the two drinks are closely related: Kossu is 38% while Finlandia is 40%, and Kossu also has a small amount of added sugar, which makes the two drinks taste somewhat different. There are also many other vodkas (viina) on the market, most of which taste pretty much the same, but look out for Ström, "The Spirit of Santa", a Finnish attempt at a super-premium vodka.
A local speciality is Salmiakki-Kossu or Salmari, prepared by mixing in salty black salmiakki licorice, whose taste masks the alcohol behind it fearfully well. Add in some Fisherman's Friend menthol cough drops to get Fisu ("Fish") shots, which are even more lethal. In-the-know hipsters opt for Pantteri ("Panther"), which is half and half Salmari and Fisu. Other classic shots are Jaloviina (Jallu) cut brandy and Tervasnapsi "tar schnapps" with a distinctive smoke aroma.
Beer (olut or kalja) is also very popular, but Finnish beers are mostly nearly identical, mild lagers: common brands are Lapin Kulta, Karjala, Olvi, Koff and Karhu. Pay attention to the label when buying: beers branded "I" are inexpensive but has low alcohol content, while "III" and "IV" are stronger and more expensive. In normal shops you will not find any drinks with more than 4.7% alcohol. You may also encounter kotikalja (lit. "home beer"), a dark brown beer-like but very low-alcohol beverage. Imported beers are available in bigger grocery stores, most pubs and bars, and Czech beers in particular are popular and only slightly more expensive. In recent years, some microbreweries (Laitila, Stadin panimo, Nokian panimo etc.) have been gaining foothold with their domestic dark lagers, wheat beers and ales.
The latest trend is ciders (siideri). Most of these are artificially flavored sweet concoctions which are quite different from the English or French kinds, although the more authentic varieties are gaining market share. The ever-popular gin long drink or lonkero (lit. "tentacle"), a prebottled mix of gin and grapefruit soda, tastes better than it sounds and has the additional useful property of glowing under ultraviolet light.
During the winter don't miss glögi, a type of spiced mulled wine served with almonds and raisins which can easily be made at home. The bottled stuff in stores is usually alcohol free, although it was originally made of old wine and Finns will very often mix in some wine or spirits. In restaurants, glögi is served either alcohol-free, or with 2cl vodka added. Fresh, hot glögi can, for example, be found at the Helsinki Christmas market.
Quite a few unusual liquors (likööri) made from berries are available, although they're uniformly very sweet and usually served with dessert. Cloudberry liquor (lakkalikööri) is worth a short even if you don't like the berries fresh.
Finally, two traditional beverages worth looking for are mead (sima), an age-old wine-like brew made from brown sugar, lemon and yeast and consumed particularly around May's Vappu festival, and sahti, a type of unfiltered, usually very strong beer often flavored with juniper berries (an acquired taste).