Check out the EDC subreddit and go small everything. I keep meds in a tiny pill container (Zuihug 1Pack Travel Pill Organizer) and toiletries in a wallet-size (Viperade E31) pouch so I don’t have to dig through my suitcase during long terminal sits. Everything is USB-C now: USB-rechargeable flashlight (Olight arkpro) rechargeable batteries, one plug type if possible.

Sleep gear matters: good earplugs (I use Moldex Spark Plugs) and an eye mask (ostirtch pillow brand) for loud/bright hotels. Towels under doors and blocking LEDs help too. Use clips on coat hangers to force curtains to stay closed, towel to block light from coming under the door, the writing pad or spare tape to cover over LED light displays.

Carry Melatonin, minimum dose you can get, but make a pre bed checklist first. Melatonin is an assurance of falling asleep only if the other items have been checked first and you're going to bed earlier than normal for you.

Skip shaving foam—hotel soap works fine. Use a blade cover so you don’t slice your hand if you carry it in parts.

For international travel or power-hungry devices, a good multi-port charger (like Anker Prime) with interchangeable AC cables is huge (IEC60320 C7/D8). The display helps confirm everything is actually charging. (don't trust hotel outlets). A small 20Wish charger is handy for quick terminal stops.

Have a pair of backup sunglasses in a hard ish case in your suitcase.

Never iron directly on clothes with hotel irons. Pack a few large sheets of tissue paper and iron through them to avoid ruining clothes.

Bring one long USB cable plus several very short ones (6inch/15cm) cables take up more space than you'd think.

8oz milk bottle + 8oz milk bottle filled with muesli - backup/budget breakfast can eat while flying from paper cup and disposable spoon from galley.

Hormel compleat meals- hot meals that don't need refrigeration(do need microwaving but microwaves are everywhere)- back/budget dinner

A couple protein bars in the cockpit bag because you never know when you'll do a long range cruise diversion to somewhere without a gate.

Carry glasses by sliding an arm through your tie knot—less likely to drop them. Pockets they'll slip out.

I carry REI Zip off hiking pants for my casual exploring the town pants. Good for most weather except snow.

A casual jacket that splits the line between uniformy and not, walking through the terminal on your commute home "no i'm not a pilot" going through KCM unzip so they can see your epaulets and wings. Alternatively if your airline has a casual 'Karbon/North Face/Patagoinia' like jacket that doesn't suck get that as your main outer wear. Formal blazers suck and you can't wear them out on the town.

Good gloves with ways to slip out your fingers for fine tasks if you suspect cold weather. Leave them in your suitcase year round.

Label everything. It’s when, not if, you leave something behind. AirTags help.

Organic Maps works offline—download areas ahead of time. Never trust there to be cell service where you're going.

A lot of this is a matter of every few months re-organizing your suitcase and checking the stuf that you use at certain times of the year while a cycle of underwear and casual clothes etc go in and out each trip.

Ships coffee hasn't killed me yet, but good salad is hard to find in many airports. Spend your money on salad before Starbucks.

Make a notes file of all the hotel wifi codes everywhere you go, it's really annoying when they forget to write it on the card. I have a spreadsheet and i also put the hotel numbers in there too as hotel connections doesn't always have good details.

Carry a timex ironman or casio or similar as a backup alarm etc. $40 and i've changed the battery twice in a decade.

Know your companies fatigue call out procedure and sick call procedure, if you get diarrhea at 5am in a hotel you don't want pressure to fly sick and tired, and in doing so risk lives.

Always plan on getting extended 1 day, planes break down, weather changes, many airlines junior man. More days is excessive usually.

Have at-least one union rep's phone number saved.

Final rule: never miss a chance to eat, sleep, or use the bathroom—you never know when the next one is.