Couple of these 3600 calorie rations are what I keep in my truck.
Life boat rations. Suprisingly good flavor, good from temps like 0-150 degrees so you can leave them in the car. and specifically designed not to dehydrate you like some survival foods.
I go with life boat rations. they store in air/water tight wrappers that are good in temps -22F to 149F for 5 years. The flavor isn't that bad either. not oreos but definitely edible. also designed not to dehydrate you like some long shelf life since they were invented to be left in lifeboats.
This. Pack for a multi day hike.
For my get home bag, I also pack Lifeboat Rations.
3600 calories. Don’t need water to eat. Not affected by heat so I can leave it in my truck. 5 year shelf life but most importantly it’s a non-thirst provoking formula so you’re not impacting yourself if you’re low on water.
Eat 5 bars of these and you're done.
https://www.amazon.com/Rations-Emergency-Calorie-Food-Cinnamon/dp/B01HPGX1QG
Assuming you can actually digest them properly, it sounds like emergency survival bars might actually work for you. There are a ton of different varieties, they're incredibly calorically dense, and non thirst provoking.
Also energy gels that athletes use could be a good option in a pinch as well.
You could easily supplement whatever else it is you're eating with these. Really dense calories/energy.
Oh, so an emergency food ration
SOS Emergency Rations. S.O.S. Rations Emergency 3600 Calorie Food Bar (Cinnamon + Coconut, 2 Pack) https://www.amazon.com/dp/B01HPGX1QG/ref=cm_sw_r_cp_api_glt_fabc_7M03RP172YTC5K4M2F70
Long shelf life and high temperature tolerance.
Has anyone ever tried survival bars? They claim to have up to 3600 calories a pack (400 calories a bar). For a hardgainer like myself, this sounds very enticing. I've tried mass gainers, only to be disappointed that one scoop is basically a large laundry-detergent cup that tastes like crap.
Here are some I've seen on Amazon: SOS Rations and Grizzly Gear