5 Ways to alter the orientation of the text in a cell
Spoiler altert – all of them are workarounds!
As of late February, 2017, the ability to rotate text is native to Google Sheets. The option is the slanted A on the main menu to the right of text wrapping.
Use a text box then rotate it
Text boxes are inserted using the drawing menu with Insert-> Drawing -> Text Box. As can be seen in the picture, they do not reside in a cell, but rather they sit on top of them. This is why the text box will not affect your row height. Once the text box is created, it can be rotated as much as you would like. After rotating it, you can then move the text box to wherever you would like it.
Skinny column with wrapped text
You can also achieve vertical text by typing the text in the cell normally. Then, you shrink the width of the column to a little more than one character wide. Next, you apply word wrap by selection Text Wrapping (on the menu bar) then Wrap. One disadvantage of this method (and all of the remaining methods) is that it alters the height of the row in which it is placed. Also, the technique requires that the column is skinny and therefore it will limit the way in which other content can be viewed if it is in the same column. Depending on how you are using the vertical text, this may or may not be a problem.
Just put the text that you want into this crazy formula. Remember to type it in both places.
=ARRAYFORMULA(CONCATENATE((MID( "Text to become vertical"; ROW(INDIRECT("YY1:YY"&LEN( "Text to become vertical" ))); 1)&CHAR(10))))
How does it work? Who cares! Just use this method if you find it easier.
Similar to the array formula, just a crazy formula into which you can insert your text.
=REGEXREPLACE( "Text", "(.)", "$1"&CHAR(10) )
I would say that you should use this formula as opposed to the Array formula simply because it is shorter and you only need to type the text once.
If you hold down the control key then press enter after a character, you will get a new line within that cell. Therefore, to enter vertical text, just type control enter after every letter. In my humble opinion, this is probably the cleanest solution until there is a true option is Sheets to rotate text in a cell. It does not require the column to be a certain width nor do you need a long formula.