Odd urine

My step son has a bad habit of forgetting to flush the toilet when he pees before he gets in the shower. It’s in the spare bedroom so sometimes I won’t go back in for a day or 2,

Well last Friday he took a shower & went to his moms for the weekend, well I went in there Sunday night and saw the unflushed toilet which was now greenish looking & moldy(I’m guessing) on the sides.

Fast forward to last night & the same thing happened.

I don’t think that’s normal for it to grow bacteria that quickly.- but I could be wrong

His dad thinks he is just not drinking enough water - that’s all he drinks here he may get an occasional soda but we mostly have water.

What do you guys think?