One method that I have found to be particularly good is using a soap with surfactants in a Hand Pump Garden Sprayer which can be found for under $20, for example here is one on Amazon that looks similar to the one I have. Fill the tank with some water and enough mild dishwashing soap such as Dawn to make a soapy feeling liquid between your fingers. I found less than one tablespoon of liquid soap per quart of water is plenty. You can experiment to find out how much is needed to be effective.
Once ready, pump up your unit well and you can spray them when they land, you can even get them in flight with a little bit of practice. Once his by the stream, they will fall to the ground and stop moving after about 30 seconds if they were sprayed with enough soapy water. If they are not dying, then you may need to add more soap to your solution or spray them with more solution.
Please be careful when doing this and cover your body with long sleeve clothing for an extra level of protection. They can get angry if provoked and go on the offence. Mornings are good because they tend to be less active at that time of day.
I believe the way it works is the soap breaks down the water's surface tension and thus when you spray the yellow jackets the water fills and covers their breathing pores and they drown.
If you want to take on a whole nest, be extra careful and consider doing it early in the morning and from a distance using a garden hose spray mixer (something like this one on Amazon) that allows you to send a stream of the soapy water a couple yards away from where you stand.
While surfactants are not great for the environment, they are way better than any typically found poisons spray cans for killing them.