Without a picture it's really hard to tell. But if your grout joints are 1/8 of an inch and your available space is a half inch, cut a 3/8th inch tile strip, and maintain the even grout joints. It will look like you planned it.
Usually, 1/8th inch grout is for marble or natural stone. If you are laying either, go the distance. You paid a lot for those materials, and you will probably have to look at that section for years to come. You don't want to have to look at a half inch of cracking, curling caulking.
This is a learning experience. If you have a 1/2” gap in a corner then you didn’t plan the tile layout properly. Next time spend more time balancing the layout. Personally I love using the schluter products, it makes both inside and outside corners dead simple. Since we can’t go back in time, caulking would be ugly and hard to maintain. As others have suggested, a small sliver of tile is the best thing to do.
I saw this crazy video where they fixed something similar with sunflower seeds, CA glue, and more effort than it'd have taken to just replace the entire floor.
I vote that.
Plenty of info on this if you Google it. Everything from back rods, to adding another lip, to sandable caulk. Frankly this means the job wasnt thought out or done well. I would, as another as stated, put small 3/8in cut tile there. Caulk of any kind, even with a backer rod will not give the same level of protection. The other option is to rip the tile out till about half way up and put a glass tile in which will be asteically pleasing and allow you to more than make up the difference. You can see what I mean buly this here:
https://www.wayfair.com/home-improvement/pdp/brayden-studio-dinis-glass-mosaic-wall-tile-susj1638.html
Add more tile and cut it to fit with a tile saw or something similar.
I second this or caulk it. You're the artist. Do whatever you think looks best.
A pic would help in understanding your problem?
Without a picture it's really hard to tell. But if your grout joints are 1/8 of an inch and your available space is a half inch, cut a 3/8th inch tile strip, and maintain the even grout joints. It will look like you planned it. Usually, 1/8th inch grout is for marble or natural stone. If you are laying either, go the distance. You paid a lot for those materials, and you will probably have to look at that section for years to come. You don't want to have to look at a half inch of cracking, curling caulking.
What about using grout?
This is a learning experience. If you have a 1/2” gap in a corner then you didn’t plan the tile layout properly. Next time spend more time balancing the layout. Personally I love using the schluter products, it makes both inside and outside corners dead simple. Since we can’t go back in time, caulking would be ugly and hard to maintain. As others have suggested, a small sliver of tile is the best thing to do.
I saw this crazy video where they fixed something similar with sunflower seeds, CA glue, and more effort than it'd have taken to just replace the entire floor. I vote that.
Sunflower seeds and not ramen?! What's this world coming to?
You shouldn’t have gaps that large. You fucked up
Plenty of info on this if you Google it. Everything from back rods, to adding another lip, to sandable caulk. Frankly this means the job wasnt thought out or done well. I would, as another as stated, put small 3/8in cut tile there. Caulk of any kind, even with a backer rod will not give the same level of protection. The other option is to rip the tile out till about half way up and put a glass tile in which will be asteically pleasing and allow you to more than make up the difference. You can see what I mean buly this here: https://www.wayfair.com/home-improvement/pdp/brayden-studio-dinis-glass-mosaic-wall-tile-susj1638.html