When I get food to go, I bring my own gear; a small cake pan for burritos, bagels, or muffins, snap-lid glass containers for salads and sandwiches, jars for soup, and a set of utensils.
If that sounds like too much to tote around, start with utensils (and consider bringing dishes when you’re feeling ambitious!). You can buy a travel set (made from lightweight bamboo in a carrying case), or just grab some from your drawer, wrap them in a cloth napkin, and toss ’em in your glovebox.
With these tools on hand you’ll have less to toss when you’re done with your meal. Just wash them and put them back in your glovebox.
Reducing your takeout trash is easy!