How to Tell Siri to Send a Text Message with Special Characters Such as Enter (Newline or EOL) - Dictation Commands
This is a question?
  End of text.


Was generated by me saying
"this is a question question mark new line end of text full stop"
 though I did have to then manually fake it into SE's markdown format 

SE isn't great for formatting tables, so this is really just in case the link ever disappears

Original Source [&amp; far easier to read] - Siri User Guide : Dictation Guide

Command                         Action                                          Before                                                                  After
New line                        Move to the next line       
New paragraph                   Start a new paragraph       
Cap                             Capitalise the next word                        I like 'cap' sunshine                                                   I like Sunshine
Caps on ... caps off            Capitalise a section of text                    'caps on' twenty types of flower 'caps off'                             20 Types of Flower
All caps                        Make the next word all uppercase                I 'all caps' love summer                                                I LOVE summer
All caps on ... all caps off    Make part of what you say uppercase             I 'all caps on' love summer 'all caps off'                              I LOVE SUMMER
No caps                         Make the next word lowercase                    I like 'no caps' Capitals                                               I like capitals
No caps on ... no caps off      Make sure part of what you say is all lowercase We like the cities 'no caps' London and Sydney 'no caps off' the most   We like the cities london and sydney the most
Space bar                       Prevent a hyphen from appearing in a normally hyphenated word       
No space                        Prevent a space between words       
No space on ... no space off    Prevent a section of text from having spaces between words      
"Period" or "full stop"         Place a "." at the end of a sentence        
Dot .                                                                           The number pi is three 'dot' one four                                   The number pi is 3.14
Point   .                       The 'point' number pi is three 'point' one four The point number pi 3.14 (note the subtle difference between saying 'point' and 'dot' dot works between words)
"Ellipsis" or "dot dot dot" ...     
Comma   ,       
Double comma    ,,      
"Quote" or "quotation mark" "       
"Quote ... end quote" or "quote ... close quote"    Place quotes around a section of text   She said 'quote' see you next week 'end quote'  She said "see you next week"
Apostrophe  '       
Exclamation point   !       
Inverted exclamation point  ¡       
Question mark   ?       
Inverted question mark  ¿       
Ampersand   &amp;       
Asterisk    *       
Open parenthesis    (       
Close parenthesis   )       
Open bracket    [       
Close bracket   ]       
Open brace  {       
Close brace }       
Dash    -                                                                       This dash is dash my dash cheese                                        This - is - my - cheese (note the difference in spacing between this and when saying hyphen)
Hyphen  -                                                                       This 'hyphen' is 'hyphen' my 'hyphen' cheese                            This-is-my-cheese (note the difference in spacing between this and when saying dash)
Em dash —       
Underscore  _       
Percent sign    %       
Copyright sign  ©       
Registered sign ®       
Section sign    §       
Dollar sign $       
Cent sign   ¢       
Euro sign   €       
Yen sign    ¥       
Degree sign ∘       
Caret   ^       
At sign @       
Pound sterling sign £       
Pound sign  #       
Greater than sign   &gt;       
Less than sign  &lt;       
Forward slash   /       
Back slash  \       
Vertical bar    |       
"Smiley" or "smiley face" or "smile face"   :-)     
"Frowny" or "frowny face" or "frown face"   :-(     
"Winky" or "winky face" or "wink face"  ;-)     
E.g. (pronounced as "e g")  e.g.    'e g' when you learn to ride a bike E.G. when you learn to ride a bike
i.e. (pronounced as "i e")  i.e.    'i e' when you learn to ride a bike I.e. when you learn to ride a bike