Little things we have access to all the time are rare, special treats

Coffee, teas, cocoa & apple cider packets
Creamer powder & sugar for coffee
Drink mix flavoring (MIO, Crystal Light, lemonade, Kool-Aid
BBQ, taco & hot sauces (Plastic bottle or single-serve packs)
Dried fruits, nuts, trail mix, sunflower/pumpkin seeds
Beef Jerky (no Slim Jims -pork products prohibited in many areas) 
Protein bars, granola bars, cereal, or breakfast bars
Cookies, crackers, chips
Ramen Noodles, Microwave Mac & Cheese, Tuna pouches
Peanut butter & jelly
Gun, candy, mints, Life Savers (chocolate can melt in some places)

Everyday Hygiene Items 

Note: Some overseas zip codes prohibit over-the-counter meds
Shampoo, conditioner, soap, & deodorant
Shaving cream & razors
Chapstick, lip balm, and lotion
Baby wipes & powder (no hand sanitizer)
Toothbrushes, toothpaste & dental floss
Visine, eye drops, & sunscreen
Blankets
100% cotton T-shirts & cotton socks (Black or white)
Shower flip-flops
Feminine products

Misc Items That Are Great To Add For Fun

Books, movies, magazines (no inappropriate or nude/seminude images)
Games & puzzles, notepads, coloring books, pens, pencils, etc.
Batteries (must be in original packaging and unopened)

Avoid Restricted Items

Aerosols, lithium batteries, alcohol products, hand sanitizer & antibacterial cleaning supplies
Cigarettes, smokeless tobacco, vape pens, & accessories
Electronics (cell phones, used electronics, transmitter radios, etc.)
Offensive or pornographic images (including semi-nudity in some magazines)
Bulk quantities of religious materials
Pork products and perishable items

In some cases, even coffee and over-the-counter meds are prohibited. The good news is you can check the specific restrictions for the zip code(s) you’re sending to here: https://postcalc.usps.com/militaryrestrictions