Despite popular beliefs, it is actually possible to train guinea pigs with the right methods and time span. For example, my piggy used to avoid the litter tray at all costs.

Wherever I moved it to, she moved somewhere else. Then, I started to use the same training method that I had used for my hamster a couple years prior. Whenever she went to the “bathroom” I would use a small dustpan I’ve dedicated to cleaning up her cage, and move the poops to her litter box. I made sure that she was watching, and that she could see where the poops were going to. After a while of doing this, she started using her litter box! I’m not saying that she’s perfectly potty-trained now, as she still just goes wherever, but most of it makes it to her tray, so I’m satisfied. Another trick you can use is getting a bigger pan, (Mine takes up a third of the space.) so that your piggies are forced to go over there if they want the space. I also moved her water bottles, hay boxes, and pellet bowl over there, because piggies usually ‘go’ where their food is. Hope this helps!