Best way to install fixed bathroom shelves
I cannot imagine how any "glue" that would hold those. But then again, you may want to inquire your local big box or hardware store and ask. Gluing right directly to polished to polished ceramic / porcelain tiles doesn't seem feasible as a practice. I would imagine if that there WAS a way to glue these like this, the surface to surface would have to be unpolished and / or ROUGH ( with small peaks &amp; valleys prepped) to get a good bond design for surface grip strength... The other route would be either porcelain / ceramic "L" brackets or of the stainless steel type.. In which case you're going to need a special drill bit to mount them...
Here's one type:

See below image / link
https://www.homedepot.com/p/Dolle-FLAC-Stainless-Steel-Metal-Shelf-Bracket-for-1-4-in-5-16-in-H-Shelves-15750/204640318?cm_mmc=Shopping%7CG%7CBase%7CD59%7CMulti%7CNA%7CLIA%7CAll_Storage_LIA|71700000048022671|58700004795392476|92700041080510599&amp;gclsrc=aw.ds&amp;&amp;gclid=CjwKCAjwkqPrBRA3EiwAKdtwk7j0A5TjHlsAAHyqs0uK06bJ6-HzDzd1PDt7Bi6BJtSYg_Ylrow0ZxoCTPAQAvD_BwE