I have the hardest time opening up bottles that have the plastic caps with the tiny grooves. Specifically Mott's Apple Juice bottles (yes, I still drink Mott's, no I'm not worried I'll die from Arsenic poisoning). They are soooooooo hard to open. Here is what usually goes down:
1. I pick up the bottle and try to open it, and think that this time, I can actually open it with no problem.
2. Hold it tight with one arm and then try to open it with the other hand.
3. Put the bottle between my knees, then try to open it.
4. Grab a shirt sleeve or paper towel and use it to cover the cap and then try to open it.
5. Skip #2-#4 and go straight for what I have found out really works: WET the paper towel, and use that to cover the cap and open it. Cotton is actually stronger when it is wet, and when it's wet, it can grip the cap better and allow you to open the cap up without making your hand hurt.