BOOM 4

Ultimate ears Boom 4. 360° sound, fits in a cup holder, waterproof, has a flap over charge port, fantastic sound and you can pair multiple together.

The tribit stormbox is a good item. I have liked some of the UE products like the Wonderboom or Boom 4

I have the tribit xsound go and tribit storm box 2. They sound much better. The ue wonderboom 4 is a smaller speaker it’s rugged but it’s still a small speaker. The sound distorts at higher volume. The ue boom 4 is a much better speaker but it’s out of ur budget. The wonder boom 4 sounds good in stereo mode. The earfun uboom is another speaker but tribit sounds better. Also check out Sony ultfield 1. It’s 20w compared to tribits storms 34w. I’m happy with the storm box 2. Which I feel is a better option. I’m not into too much of bass and prefer clarity and both my tribits fulfill this.

Probably a UE Boom 4 because it fits more easily in the car and sounds good

A UE Boom 4 works great in the car

i second the bose soundlink max for your use case. BUT you'll want to check out its weight and dimensions to be sure it's the right size. "fit in my backpack" can mean a few different things depending on the size of the backpack and how much space you're happy for the speaker to take up haha. if the max is too big, consider the bose soundlink flex (2nd gen), or one of the ultimate ears boom/megaboom 4 speakers, or maybe the JBL charge 6. but yeah size is very important here when it comes to narrowing down your options.