In a medium mixing bowl, combine mayonnaise, olive oil, white vinegar, water, and Italian dressing.
Mix all the ingredients well, making sure there are no lumps.
Taste the dressing and adjust the seasoning to your liking. If you prefer it sweeter, add some keto-friendly sweetener. If you prefer it tangier, add more vinegar. If you prefer it saltier, add salt.
Once you're happy with the taste, transfer the dressing to a clean, airtight container and refrigerate for at least 1 hour before using. This will allow the flavors to develop and intensify.