Let's break it down:
* petit pour boire du lundi: This could be interpreted as "something small to drink on Monday." It's likely referring to a beverage.
* depose attaque la semaine: This part is very unclear. It could be a misspelling of "dépose, attaque la semaine," meaning "deposes (something), attacks the week." However, this doesn't quite make sense in the context.
* bon pied bonne journée: This is a common French expression meaning "good start to the day."
Possible interpretations:
1. A toast on Monday: The phrase might be a playful way of saying "let's have a small drink on Monday to start the week off well."
2. A motivational phrase: It could be a motivational phrase, encouraging someone to tackle the week with energy, perhaps even with a small drink to boost their spirits.
3. A miscommunication: The phrase might be a result of a misspelling or misunderstanding of French grammar and vocabulary.
Without further context, it's difficult to determine the exact meaning.
If you can provide more information, I might be able to give you a more accurate interpretation!