Tongue twisters are more than just silly sentences. They are a great way to get pronunciation practice! You can use one of my favorites to practice two very important aspects of English pronunciation: weak forms, and connected speech.
"Can you can a can as a canner can can a can?"
Weak forms are words or syllables that lose their strong vowel sounds when they are unstressed. For example, in questions with 'can', the word 'can' is unstressed because it is functioning as an auxiliary verb. So instead of an open 'a' like 'cat' sound, you should pronounce it without a vowel sound at all! Imagine you are just saying the letters 'c' and 'n' together.
So in the above tongue twister, the first 'can' and the fourth 'can' are weak and just sound like 'cn'.
Some other examples of weak auxiliary verbs are:
Have I lost my keys? = "Hv I lost my keys?"
Do you know where they are? = "D you know where they are?"
The second important pronunciation rule in our tongue twister has to do with connected speech. In spoken English, when one word ends with a consonant (b,c,d...) sound and the next word begins with a vowel sound (a,e,i,o,u), we connect the two words together like this:
You should try to pretend that you are saying just one word that sounds like 'cana'.
In our tongue twister, many of the words connect - notice the longest connected part:
Can you can_a can_as_a canner can can_a can?
When you say this, it should feel like you are saying just one word!
"canacanasa" not "can. a. can. as. a."
This whole sentence is connected!
There are many other features of connected speech that you can practice to improve your pronunciation, for example, some vowels create a sound that connects to the next word - "blue eyes" sounds like "blu-wise" but it's easier to focus on consonant to vowel connections at first.
Now, try the whole tongue twister again with both rules:
Can you can a can as a canner can can a can?
cn you cana canasa canner cn cana can?
You can practice these pronunciation rules more with any text by marking the connections and practicing reading out loud, but it is especially useful to practice with a recording that has a transcript.
For example, ted.com is a website with tons of recorded speeches with transcripts. Find an interesting speech by a native (or very high level) English speaker and print the transcript. Listen to the speaker talk and mark all the connected words you can hear in the transcript. Then practice reading it with them until you can go as fast as they do! Connecting your words will really help you to speak more quickly.
Then you can mark all the weak forms you can find (auxiliary verbs, like the first and fourth 'can's in our tongue twister, articles, unstressed syllables in longer words, etc...) and practice reading those properly as well.
If you practice these two pronunciation features with my favorite tongue twister, then with a recorded speaker and a text, I guarantee your English fluency will improve and you will feel more confident with speaking. You will improve even more if you practice reading to a teacher and ask for their feedback.
(The tongue twister means: "Are you able to put things in a can they way that a professional can factory worker is able to put things in a can?")