First, measure out all your ingredients into small dishes you can pour into the Bowl of Candy, because the Candy will be begin to harden quickly, you'll need the ingredients ready to go to follow the recipe, and won't have time to get them together after you start. DO NOT SKIP THIS STEP!
In a Microwave safe medium size bowl, add the Sugar, Corn Syrup, and water, and stir together. Place in the Microwave for 6 minutes, on HIGH, stirring half way through, at 3 minutes.
Line a Cookie sheet with Parchment Paper, and set aside.
Remove from the Microwave, and add the Butter, and Microwave for 1 minute.
Remove Bowl, and stir in Mini Pretzels, salt, and vanilla, and Microwave for 15 seconds.
Remove Bowl, and stir in Baking Soda - mixture will be light and foamy.
Quickly, pour the Brittle out onto the Parchment Paper lined Cookie sheet, and spread out into a thin layer with spoons, or forks - you'll need two utensils to spread the Brittle. Immediately, sprinkle the M&M's on top of the Brittle, lightly pressing them down into the hot candy.
Let the brittle cool for about 45 minutes to 1 hour.
When the brittle is cool, break it into pieces.
Serve and Enjoy!