You'll want to make your vinegar ahead of time so that you can cool it in the fridge for about 15 minutes before adding it to the vegetables to keep them firm and crisp.
In a small pan add vinegar, water, salt, and sugar.
Turn stove to medium heat, mixing occasionally until salt and sugar dissolve. Do not let the mixture come to a boil. This should only take about 5 minutes.
Let cool in the fridge so the veggies stay crisp when you add them.
Veggies
Chop all of your veggies and put them in a glass jar. Add the cooled vinegar solution so that it fills up the jar.
Set your veggies in the fridge for at least 2 hours or overnight and enjoy the next day or for up to 2 weeks!
Notes
You can add any vegetables you want to the vinegar. Some of my favorites other than cucumber and carrots are green beans, red onion, and mushrooms.