The Quart-Sized Mini Bar
I thought this was obvious, but I talk to a lot of people who are wasting their TSA-approved quart-sized bag on things like shampoo and conditioner. (come on, you can get these free at a hotel even if you're not staying there - just ask the front desk).
So, if you've been blind also, hopefully this improves your next flight / travel.
Step 1: Get a quart-sized plastic bag.
Step 2: Get a set of boston round bottles - and go to your bar, or pick up a good bottle of booze. Me? I go for high proof bourbon or scotch. Maximizes the 2 oz. size of the bottles with something you either need to punch you in the face to handle a long flight, or that you can add water or in-flight mixers to your personal taste. (e.g. Blanton's Single Barrel or Laphroaig Cask Strength).
Step 3: Fill the bottles, and put those bottles in your quart-sized bag. If you've ever been in college, you might have a few flask funnels laying around, but if not, get one. Cheap and handy to fill your bottles next time.
The meh way to do this is just to buy airline bottles at a gas station (short-term fix, but ideally, I recommend using your own bar. Better quality options, less plastic waste, and cheaper by the pour for you).
Note: It is not technically permitted to drink alcohol on a flight that a flight attendant has not served you, so if you use these, wait until you are discreet and as with most hacks, just don't be a dick about it and be nice to people and you get away with far more. I prefer to order a water, club soda, or ginger ale, and use the spent ice to do a little pour over. And of course, don't forget to down one before you even board just to get a head start, and save one for as soon as you get to your AirBnB/Hotel/Friend's Couch.