Well there are a number of ways to do it. Depends on your overall setup. What does thecage sit on? Is there room for some kind of bucket or container? Posting a pic of your current setup is helpful.
I recently did a cage drainage system with a lllreptile drainage pan and tray. There is a thread on here with some ideas on that type of system. On my phone so i cant hot link it but i think its called cage drainage system. Lol. Do a search there are a bunch of ideas floating around.