I can't help with the cheap red dot sights, but I've bought a few brands.
The top brand (that DOESN'T break the bank) is Holosun. They have both cheaper models and more expensive models, all very high quality. Actually, the Holosun sights can easily compete with the higher dollar ($600 & $700 brands). There's a guy on YouTube that crash tests various red dot sights. He put the Holosun sights right on top of the list for holding up to the accidental fall. Nobody is immune to the accidental mishap. The cheaper sights, can't come close.
Vortex is a decent brand, "some" UTG red dots are ok. A little higher up, Leupold has the "Delta Point Pro" which is high quality and very easy to use. The Burris Fast Fire II, III are fair priced sights for some amount of quality. SightMark has a couple of reasonably good ones. Sig Sauer has some that are good, but not in the $100 range. But I like the Leupold over the Sig Sauer.
One thing to note too, having JUST a single dot on the screen can be a chore to find quickly. Some (Holosun for one) has put a circle around the dot to make finding the 2mm dot easy to find. The dot is small to not obstruct the target as many do, and the circle is also large enough to not get in the way.
I've found over the years, spend the money up front, that way, you normally (NOTHING is perfect) don't have to spend multiple times when the original quits doing what it's supposed to..!
Mike