Pasting Spreadsheet from Excel to Outlook, chart gets distorted

If you're conceed about the presentation of the workbook, I would print a PDF and then send it as an attachment. Screenshots of a figure are generally a decent way to accomplish this as well (use the PrSc and then paste into MsPaint to crop/edit if desired).

If you want to send the dataset, Export it as a CSV (or other data format) and attach it, too.

In Office2016, both can be accomplished by selecting File->Export (File in the ribbon, Export in the popup sidebar). Use the "Change File Type" to select which you want.