sing. ochi / ochiul
plur. ochi / ochii
sing. ochi / ochiului
plur. ochi / ochilor
How can a non-native speaker best reproduce the terminal sound here? Perhaps a hiss?
Say the one-syllable word "cheek" (cheek). Now say the two-syllable word "cheeky" (chee-ky).
And now, try to alter how you say "cheek" as if you'd want to say "cheeky" instead but you ran out of extra syllable slots, so you compress/shorten the "-ky" part and you kinda just whisper the last vowel, so that you're able to cram the entire word in just one syllable.
If you've done it right, the last part of "cheek" will differ from the last part of this new word (that you're trying to pronounce) in just the same way that the FIRST part of "coot" differs from the FIRST part of "cute". That's the terminal sound you're looking for.
Just for reference, see (hear?) the first two pronunciations (the ones from RazvanB and from Salerosa) of "ochi" here: https://forvo.com/word/ro/ochi/.
Think of it as the ghost of an /i/. For this exact word, try to say "oh-key"
* in just one syllable, suppressing the final vowel as much as you can.
*of course, "oh" is not really the Romanian vowel represented by "o".