I am trying to do a liquid simulation where the fluid is pouring into the glass but I'm not able to make the glass look realistic... Below are some examples:
Edit: Here is the .blend file
Blender Stack Exchange is a question and answer site for people who use Blender to create 3D graphics, animations, or games. It only takes a minute to sign up.Sign up to join this community
You're doing something reasonably complicated here, and it seems like this is one of your first projects. So this might be a weird and meandering answer...
Glass is weird. There have been multiple times I have had to sanity check myself, and it's always turned out that I had just never spent that much time looking at that particular thickness of glass, or something.
Here's a picture from real life where I just couldn't believe what I was seeing in blender (a highlight reflection from both the outside and the inside of the glass), and it's the second time that such a realization made me take a picture of the light interaction so as never to forget it...
although I do seem to have lost that first photo...
What I'm trying to say with all of this is that... You made a geometrically perfect glass object and you set the camera at an exact 45 degree angle, also the background is a gray void so glass objects just look a little strange anyway. You've never seen that in real life, but I would say it's totally probable that if you did, it would actually act as you see there.
Looking at your glass, it's a thicc boi and it has an inner structure that doesn't match up with the outside.
That's not your average glass, and so it's not going to have a familiar appearance.
If we add a bevel to match the inner structure up with the outer, I think you'll find the appearance much closer.
(By the way I replaced your material with just a Principled BSDF.)
And so hopefully that's illustrative of what I was trying to say earlier, but actually we could delete all of the inner structure and use a Solidify Modifier and that makes it much easier to adjust the thickness and get the appearance you want.
I didn't rebake the simulation here, so the glass is not full, but I think you get the picture. The appearance of glass is difficult, sometimes especially in this engine, and in blender it's a combination of a lot of things.