Ugh, sorry, I can’t eat tomatoes. Here, “Ugh” is a/an-

We use interjections to express emotions such as pleasure, surprise, shock and disgust. Most interjections are just sounds, rather than actual words, and come at the beginning or at the end of what we say. Interjections are more common in speaking than in writing:
Ouch, it stings. (expresses pain)
You’re going to the Maldives. That’s a long way, wow. (expresses surprise and wonder)
Hooray, here comes the bus at last! (expresses delight)
Ugh, sorry, I can’t eat tomatoes. (expresses disgust)