Sima is the official drink of Vappu in Finland, celebrated every May 1st. It is a lovely drink, both sweet and tangy with a nice fizz to it. It’s very simple to make, and the key component to making it is … Patience. Yes, patience. It takes time for the drink to ferment, and so for those who would like to enjoy this wonderful, seasonal drink on its traditional day, a little bit of planning ahead is called for. I would start making this at least a week in advance since it will take at least 4 days for the second fermentation to fully ferment.