Traveling via road trip is one of those times where I typically would use a lot of disposable items, mostly related to food, but also small toiletry items, paper hotel bills, bottled water, plastic bags, etc.
Planning for traveling with less trash takes some thinking ahead, and some different choices, but it's really not that hard. Let's take a look at my thought process by category.
Note: This post contains some affiliate links. Some are for items I bought, liked, and recommend. Other links go to items similar to things I got as gifts/swag from conferences.
Food:
This is the toughest. Fast food is so easily accessible and delicious, but it does generate a lot of trash. Choice is my tool here. I can choose food places that serve on reuse-able tableware. Panera is a favorite option for that reason, but there are also lots of local restaurants worth trying. Taking the time to get off the highway, and sit down at a restaurant is a good way to make less trash and enjoy the trip more. Google maps now makes it possible to find good food options that aren't within sight of the highway. And when friends tell me about good places to eat in their towns, I add those to my "want to go" saved section in Google Maps.
Of course many places still want to hand me a plastic cup, so I plan ahead and keep a re-useable tumbler cup in my car. This comes in very handy. I can use it for a drink at a fast casual restaurant and also fill it with water in the hotel lobby. Plus, sometimes a restaurant won't even charge me for the drink if I brought my own cup.
Snacks are readily available in bulk bins. I bring them along in canvas bags, or Stasher bags. This also helps me not spend money at convenience stores.
Plastic utensils eventually show up in every road trip, so I bring a fork and spoon wrapped in a bandana. The silverware stays clean and the bandana is a re-useable napkin. I've never really needed a knife, but if I think I might need it I could add that to the kit. Some people like a bamboo utensil kit to save weight, but I tend to pack light enough that it's not an issue. Note: If you are getting take out food, you need to specify that you do not need utensils.
Hotels almost always have a coffeemaker and paper cups to go with it. My camping mug was an unexpected gift from an edtech vendor. I didn't think I would use it much, and then I thought about making tea in a hotel room. I would have to use a paper cup provided by the hotel to fit into the one cup machine. I remembered the camping mug and brought it along. It fit perfectly in the coffee maker, and I didn't have to trash a paper cup. One of the things I like about this mug is that it has no handle, making it easier to pack. The lid means I can use it to pack small items too. Apparently, it is hard to find one without a handle. This Yeti one is similar though.
Water:
I mentioned filling my tumbler cup with water from the hotel lobby. On road trips I also usually bring 1-2 large water bottles that I filled at home. If needed I can refill these while traveling. Often I travel for conferences and there are usually water stations set up I can refill from. This way I never cave to the $7 bottle of water in a hotel room. (I'm not kidding. That was the actual price of the bottle in my hotel room a few weeks ago. And it was not a very fancy hotel.)
Toiletries:
Ahh, the travel sizes. They are so cute. I used to love going to the wall of bins at the drug store and paying a premium for little bottles of shampoo, sunscreen, and other assorted mini versions... of things I already owned in larger sizes. Of course I also owned cheap tiny refillable bottles that leaked sometimes. And I subscribed to one of those beauty samples boxes that sent me 5-6 small sizes of things every month, many of which became "save for travel" items. Then I would get out on the road and find out I didn't really like that product after all.
It was in 2020 that I bought my set of Cadence capsules. Fair warning, these are pricy, but they are great for travel. I can easily fill them with the products I already use. (No more buying expensive travel sizes of items I'm not sure I'll like.) And, if I consider what I've saved by not buying travel sizes, these have paid for themselves. Plus, I always have exactly the same products I use at home. No surprises. These capsules never leak. Really, the caps fit tight and I've never had a leak issue through lots of flying and driving. They are adorable, and they magnetically stick to each other to keep them together. The lid labels are also magnetic and swap-able. 
The printing on the lids is often hard for me to read without my glasses, not ideal for the shower, so I swap the label tiles from different colored containers to create color combinations I can distinguish. Each original capsule is .56 oz, which is not large. Now, they make bigger versions too, but I have never felt the need for a larger size.
Part of the reason some people say they want larger Cadence capsules is to carry shampoo. Since I cary a piece of a solid shampoo bar, I don't worry about that. I wrote about my favorite shampoo bars here.
Grocery Bags:
In any road trip there comes a time when I need to buy something, so I always cary an expandable bag. If I'm in my own car, there will also be standard sized re-useable grocery bags in the trunk, but the expandable bag is great to keep in my purse. I have a really compact one that was swag from a vendor a long time ago. I've tried to find similar versions of it to give as gifts. These were as close as I could get. I like that they come in a three pack. I put one in my daily backpack and gifted the others to family members.
Paper:
A lot of the paper is already out of our travel process these days anyway. Think boarding pass on your phone and hotels that email you the bill. (That sentence would make absolutely no sense to my grandmother, who was an amazing traveler in her day.) I still manage to cut a little more paper here and there, like refusing the map of the local area the hotel receptionist tried to hand me and choosing paperless receipts.
With a little forethought, some planning, and by brining along just a few extra items, I was able to remove a lot of the trash from my road trips and make myself more comfortable in the process.
