Since Google Sheets is a spreadsheet application and bullet points are rarely needed, the option to create them was left out from the toolbar. However, Google Sheets does include support for bullet points.
There are two ways to add a bullet point to a cell in Sheets.
Using a shortcut
On PC: Hold the ALT key and press 7 (on the numeric keyboard)
You can also follow with ALT + ENTER to insert a line break if you wish to add multiple bullet points inside the same cell.
On Mac: Hold the OPTION key and press 8
Follow with CONTROL + OPTION + ENTER to insert a line break.
Using a formula
The CHAR function in Sheets returns the character specified by the code number.
Paste the following formula in the cell in which you wish to add a bullet point:
If you want to create a bullet point list, you can drag handle to the other cells and the formula will follow.