After reading all the reviews on multiple cups, and ignoring the Chinese knock offs as much as possible, I bought two 20 oz tumbler s, a Yeti and The Beast, and put them to my tests for my two needs.
I left the two cups on the counter overnight, and the next morning I filled them up with boiling water (boils at 198 degrees where I am).
I then filled both cups at the same time, put the lids on, opened the drink opening and tested the water.
Starting temp - 186 degrees
One of the first things I noticed was the lid on the Beast cup pushed itself up due to the pressure caused by the VERY hot water. This was not occurring on the Yeti. So that means that the Beast cup was sealed tighter, but it also means that the lid being pushed up could allow for spills. After the 2nd hour of testing, and pushing the lid back down, the Beast lid stopped pushing up.
I left the water in for 8 hours, testing at the top of each hour passed. I only opened the drink ports to take the temp and then closed them back up.
After 8 hours the water in BOTH cups was the same - 110 degrees.
So now I tested the spill factor.
At first I used cold water, filled the cups and turned them over.
The Beast cup never lost a drop. The Beast has a drink port that seals by pushing it down into the lid.
The Yeti with the magnetic slide lid, dripped but it didn’t gush. So if you were quick to grab it, you would t lose much.
THEN I tested with HOT water.
BIG DOWNSIDE for the Beast. See video attached.
I filled both cups with hot tap water, which at my place is 125 degrees. I then held the cups upside down and the Yeti I even shook upside down.
So the Yeti did the same thing with hot as with cold. It only lost a few drops, even when shaking it.
The Beast did what I thought it might - in under a minute the lid came off! This was due to the lid pushing itself off due to the pressure.
Yes, the Beast is 100% spill proof, as long as the liquid in it does not cause enough pressure to push the top up. If it is too hot, and you knock it over, there’s a very good chance the entire contents will dump out.
If the Beast had a pressure release - so let’s say a very small hole drilling in the lid, then this could most likely be avoided.
Even though the Beast is $10 cheaper, I’m gonna go with the Yeti since I put very hot drinks in them.
Note - in the pics the Beast is on the left and the Yeti is on the right.