Abnormal Rat Behavior?

So, I've had these two rats for about two months. They're mostly socialized, like we can play with them and whatnot without them pooping all over us. The problem is when they're in their cage..they urinate usually only where the water bottle spout is located, and they also poo in the urine, making a lovely mess that I think they enjoy playing in while we sleep, because they usually smell like..well, pee. We've tried to litter train them using several methods, and nothing seems to be working, I swear to you, the other night I watched one of the rats lift the litter pan and DUMP it out, then throw the darn thing across the cage. Oh, and for the past couple of days, they have been taking craps in their hammock during the day when they have to poo while sleeping, I guess they're too lazy to go down to the bottom of the cage and they don't mind rolling in their own crap. This is ridiculous, I can't bathe them every day, but I can't stand the smell of them, either! I got rats 'cause I thought they'd be easy to potty train and from what I've read, they're supposed to be fairly clean and not urinate where they drink and poop where they sleep. If it matters, they're both boys, and they're both about three months old, and we got them from a shoddy pet store where they were born.