What are your best tried and true life hacks for the field?

Good waterproofing bags, whether they be civilian or military. My personal favorite are sealing bags that marines are issued. 2 large ones for the contents in the main ruck, and 1 each small ones for the sustain mentioned pouches. All other additions are simply personal preference, but nothing pisses off a grunt more than finding his creature comforts that he brought to the field were ruined by some rain during movement

Canned foods: raviolies, beef stew, spaghetti os. MREs strictly for movement and even that is broken down into bare essentials.

Gummy bears (3-5 lb. bag), car charger for LMTV 12 volt adapter, sock liners for so much time on my feet, a few books, taco bell mild sauce, cabellas cot, fitted bed sheet (brown) to cover all my gear while I'm away, (keeps dirt/dust out, brown tarp, (for my area. Keeps down the dust/dirt) and of course my propane burner for making coffee. I know there's more but I can't think of it all at the moment. I know them when I'm packing.

Probably all very dated now ,but a few from the old days PRC 25 battery bags kept cigarettes and mail dry,commo wire for poncho hooches,peanut butter from C rats mixed with a touch of bug juice makes a smoky substitute for heat tabs,the wire from the C ration boxes could be used in a pinch for a rifle cleaning rod,gas mask carrier handy pouch for M 60 ammo.

The best and most important was the woobie. Best thing ever. I still have and use mine while camping to this day.

It may sound odd, but I would also always bring a paperback book or two. It may be a little bit of extra weight, but they always got used. During longer field problems, the paperbacks would get read a couple of times by everyone in the section. Typically, they would be falling apart by the end of the FTX.

Double or triple wrap everything. Put my clothes in the weather proof bag, and that inside a garbage bag. Sleeping bag inside a garbage bag, and line my ruck with one. Don't like wet gear.

We were in the field and it was raining. My turn to sleep so I took my waterproof bag and put it over my head to keep the Rain off of my face so I can get some sleep.

I pack all my snivel gear. pack things to read. my poncho liner always goes. small bag with extra cleaning supplies in case I lose stuff or get separated from my duffle. includes tooth brush soap,towelettes. toothpast deodorant small bottle shampoo. etc. extra sandwich or larger size zip lock.extra pens pencils small notebooks. small snack back (ziplock with things like trail mix )peanut butter crackers. small flashlight extra batteries. one of those knife tools with plier appliance. gloves.instant coffee. gum

For cold weather there is nothing warmer than your pt jacket under your uniform (non visible) will work better than a northface jacket and also your pt shoes inside your wet weather boots, warm feet always

Lil Esbit stove & Stanley 20oz lil metal cup/pot (can be bought at walmart $20)... good for making coffee (which I put in empty pill containers) ramen noodles, soups pork beans, dehydrated food etc,, the fuel tabs last about 8 minutes I add lil twigs to make hotter faster. and it does not take up much room either the esbit stove is small and can hold 4 feul tabs.... inside the Stanley Metal cup are 2 more lil thick plastic cups, and there is room left for a lil metal crkt spork & p58 can opener plus room for more fuel tabs!!
oh put some foil folded up in bottom of esbit stove so if it is windy ya can make a wind screen help keep flames on cup and last longer