Neologisms are made-up words. Be very careful with them. If you’re good at them, terrific. (Heinlein was great at them. I got all the way through The Moon is a Harsh Mistress before I realized that tanstaafl wasn’t a perfectly good Dutch word, and I used to live in the Netherlands.)
If you aren’t good at them, you can make yourself sound silly.
In particular, watch out for what Damon Knight called “calling a rabbit a smeerp.” Just because you call a long-eared short-tailed lagomorphic mammal with long hind legs a “smeerp” doesn’t make it alien.
We all write sf in standard English, unless we are Anthony Burgess (who did made-up dialect well), or some other people who do it not so well. There’s no particular reason to translate words for time, distance, and food into gibberish. (I don’t know why time, distance, and food are so susceptible to this in science fiction, but they are.) If your characters are drinking coffee, have them drink coffee, not “klaa” or “jav.” Coffee’s been around for more than a millennium. It’s probably going to last.
Besides, as a linguistically oriented friend of mine pointed out with some exasperation, almost all the made-up words in science fiction written by English speakers sound like made-up words derived from English.