The original film (reviewed here) was dumb but still occasionally clever and entertaining. This one is just dumb. In fact, the one clever idea they had was to call it Hot Tub Time Machine 3, but the studio wouldn’t let them. John Cusack wisely stayed away this time.
The remaining characters travel into the future this time, and a lot of the jokes are based on current trends taken to greater extremes, but this doesn’t really work, at least not here.
The only scene I liked was one in which the protagonists stand in front of a mirror observing and commenting on their future selves. (Otherwise we see them as they are today.) This scene was created by letting the actors improvise and then selecting the best bits in editing, thus achieving protection from the script.
There are a few other non-awful moments, but otherwise it has the feel of not-very-good fan fiction set in the Hot Tub Time Machine universe.