"A cup of coffee and a jelly doughnut, please."
Translation:Kuppi kahvia ja munkki, kiitos.
"munkki" is not "jelly donut" . "Munkki" is just "donut". "Jelly donut" is "hyytelö munkki." Donuts with holes are either "munkki" or "donutsi." Donuts without holes are only "munkki." Donuts with holes and jelly are "hyytelö munkki" or "hyytelö donutsi." Donuts with no holes and jelly are only "hyytelö munkki." Please stop putting "jelly" in the English translations of "munkki." Jelly is irrelevant and including it here makes the translation wrong.
Munkki is a holeless donut and donuts with holes are either munkkirinkeli or donitsi. Holeless donuts with jam are hillomunkki and donuts with holes and jam are just donitsi because that's too fancy for a munkki. Except donuts without holes, with (usually pink) frosting and jam filling are berliininmunkki.
Hillomunkki are munkki with Jam. The world jelly only relates to jam in the USA, in the rest of thr English speaking world Jelly is what the Americans refer to as jello,
It's one whole munkki. The -a ending in "kahvia" is a partitive marker. In English, in this case, you express this by saying "one cup OF coffee", since it's not "one coffee" (yksi kahvi). If you only wanted a piece or a slice OF munkki, you'd say e.g. "pala munkkia" (which nobody would actually order) and use the partitive.