In a bowl of your mixer whisk together egg whites (4), sugar (1cup), salt ( pinch) and vinegar (1tsp).
Pour water into a sauce pan, few inches in enough. Bring water to simmer. Place a bowl with egg whites and sugar over the simmering water. Stir with a whisk. Stir constantly.
Sugar will gradually dissolve and you will be left with white soapy mixture. It will take around 4-5 minutes. You can test if all of the sugar is dissolved by dipping your finger into the mixture and rubbing it between your fingers. If it's smooth sugar is dissolved.
We need to bring egg white to safe temperature. Attach a candy thermometer onto the bowl, continue stirring, till thermometer reads 160 - 170F.
Remove the bowl from the simmering pot and immediately start beating with a wire attachment. Start on low speed and gradually increase the speed to medium-high. Beat until thick, glossy peaks are formed. Beat in Vanilla Extract. Color as desired with gel food coloring.
Notes
How to Use Swiss Meringue?
You can use Swiss Meringue to make meringue cookies.