An idiom that means to make up stories or excuses, especially those that are not true, and are just false excuses you give when you try to justify/save yourself.
Maybe similar to feeding crap/bullsh**
Not an idiom, "pretext" seems to fit
A reason or excuse given to hide the real reason for something, a fictitious reason given in order to conceal the real one. TFD
It was a pretext for not joining us.
This answer is from the point of view of the person to whom the excuse is given: fairy tale
John told me another fairy tale about why he can't finish repairing the car until next week.
fairy tale from Oxford Dictionaries
A fabricated story, especially one intended to deceive
An idiomatic expression is to tell a cock-and-bull story :
a story or explanation which is obviously not true.
- She told me some cock-and-bull story about her car breaking down.
(Cambridge Idioms Dictionary,)
Here are a few:
fob someone off [with some excuse]
brush someone off [with some excuse]
Although not explicitly stated anywhere, spin a yarn has some connotations of very slight deception, in that someone spinning a yarn wants the listener to believe what they have to convey.
To tell or create a story, especially one which is far-fetched.
You could refer to this as a song and dance:
a long and often familiar statement or explanation that is usually not true or pertinent
(Merriam-Webster)
I'd use "fibbing" here.
From WordNet (r) 3.0 (2006) [wn]:
fib n 1: a trivial lie; "he told a fib about eating his spinach"; "how can I stop my child from telling stories?" [syn: {fib}, {story}, {tale}, {tarradiddle}, {taradiddle}] v 1: tell a relatively insignificant lie; "Fibbing is not acceptable, even if you don't call it lying"
Being 'economical with the truth'
Being 'economical with the truth' means that you've used 'the truth' very sparingly - which means that you might have just used a little bit of it - and often have omitted important details, to serve your own end, or you have embellished the story, to your own advantage.
economical with the truth - avoiding stating the facts, or lying https://dictionary.cambridge.org/dictionary/english/economical-with-the-truth