This one is sort of very specific and niche, but as a caregiver of someone with an ostomy, you can take a roll of this disposable plastic produce bags from the grocery store. Terrible for use as a produce bag because they're plastic and disposable and whatnot, but for bag empties when you need to use something disposable no matter what? They're invaluable.
Also doggy poop bags. Great for that. Just grab one of the small almost empty rolls, and tell the cashier "I'mma take these" and no one gives a shit
I use a half gallon insulated metal water bottle/jug and it's incredible. I love it so much, and I couldn't go back to even a normal sized one. I drink easily a half gallon a day now. I'm about to upgrade to a 1 gallon, because the lid on my half gallon is difficult to open, and the 1 gallon has a much better lid. I know it seems ridiculous, but it made a carry bag for it with a strap to wear almost like a messenger bag. I can carry all my shit and get hydrated at the same time. So fantastic.
Also, buzio is the brand on Amazon (I know. God, I know, but we don't have a lot of options where I live. If anyone knows a better one, I'd love to hear it). They're great. Everyone in my family has one in different sizes