The correct word is "lămâie" which is only slightly different than "lămaie", which is slang for the uhhh, physical evidence of a male orgasm. So I've ordered drinks "with ice and" the other substance, until I managed to get the hang of emphasizing the "â" sound.
If I'm a little drunk I just say "with fruit" and then they say "with lemon you mean?" and I say "yes" and the problem is solved ;)
Pax Night and day you can find me Flogging the Simian