push all the furniture in one room back against the walls so you have open space and can't break stuff.
empty bottles and a ball for bowling
empty boxes to use as building blocks, just really big ones (cake mixes, etc, that aren't empty work, too! but empty soda boxes or moving boxes work even better)) (build a big wall to topple over or crash thru, build a ramp to jump hot wheels over them, build a "fort"
If you don't mind a mess, packing peanuts are a blast to dump out
use electrical or masking tape to make roads all over the floor. Some boxes can become houses and stores, and you can drive your hotwheels thru the roads (set up is as much the fun of this activity as playing, in my experience)
beach ball volleyball
if you have swim rings (or those floating noodles, you make rings out of them by making a circle and taping the ends) yu can set up an obstacle course with the "tires", a blue towel "water hazzard" you have to jump, a tunnel you have to crawl thru, etc.
I was stuck inside with 2 kids for 5 days once. I got desperate.
Good luck,