I am 95% convinced it is a variety of Jade plant..
not the "common jade" houseplant, but a close cousin..it's a succulent, like a cactus.
Doesnt need much water..best to let it dry out completely between waterings.
Give it a good drenching, then dont water again for a long time! weeks, even a month..
let it dry out a lot before watering again..
over watering will kill it..also needs the brightest window you can give it, direct sun is fine.
Jades are very "easy" houseplants..stick it in a window, water rarely..that's about it! :)