Amazing Book Read as a Teen!

This book was wild y'all! Aliens land on earth, they slowly abduct a group of people! These people once inside the spaceship are exposed to a massive environment an entire other world filled with challenges and struggles. But something's off they notice they never get tired, they never seem to get hungry either... they even don't have to use the restroom! They realize they are inside some kind of simulated environment...i don't remember many details as this was over 25 years ago i read this book but the ending definitely stuck in my mind. The humans once aware of their simulated environment somehow manage to break free into the actual spaceship of the aliens, but things are even weirder, the aliens are not humanoid at all instead they are a liquid based species not susceptible to the same laws of physics as us humans allowing them to travel much faster than we ever could...If anyone read this book i would love to find the name and author again! Thanks ahead of time for any help given!