Today's Japanese

sushi kudasai = (May I have) sushi, please(?)
"kudasai" means "please (give me something)" when you have a noun before it. If you use it with a verb, it then becomes "please (do something)".
Technically, you are supposed to add "o (an object marker)" after the noun. "sushi o kudasai" would be the grammatically correct form, but to make things easier and more casual, you can skip "o" when you're speaking.
Here're some useful (?) nouns in Japanese.
sushi = sushi
gohan = rice (because rice is the basic food here, gohan (= rice) could also mean a whole meal)
shishi kababu = shish kebab
hashi = chopsticks
OK. I think you now know the basic structure of asking for something in Japanese. So please repeat after me.
"wasabi ice cream kudasai!!!"