In general the
dutch word "Sappie" or "Sap" refers to a 500 millilitre can of cheap
beer. It's mostly used when a person uses the key to open a drinkhole at the bottom of a can, allowing air to flow into the can when opening the lid of the can, resulting in optimal drinking conditions.
More specific use of the word "Sappie" refers to the 7.9 percent ABV
beer from the brand Perlenbacher: Perlenbacher strong