Possible Options:

Naturalistic Speech Intelligibility Training:

• Sit with the child during a natural conversational activity (anything that the child wants to do when he will talk with you).  Use his interests to guide the activity and the conversation.  If possible, bring in materials that will elicit certain sounds or structures but if he’s not interested, just use what he has.
• When the child makes an error, recast what he said: repeat it back but fix the errors.  Focus on correcting grammar, syllable structures, and speech sounds.  Keep utterances short and provide pauses and opportunities for the child to repeat (but don’t request that he do).
• No prompting for imitation or working on motor plans.
• Offer many models of the correct way to use the recast.

Example:

Child: “dat my brella”

Adult: “That’s my umbrella.  You’re right!  That’s your umbrella.  Umbrella.  I have an umbrella.  I use it when it rains.  That’s my umbrella.”

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/219624/DFE-RR247-BCRP10a.pdf (go to page 89)

Core Word Approach:

A short list of common words that the child mis-pronounces is assembled.  These words are practiced in isolation and then the child gets to play with whatever he wants (as long as he will talk with the therapist).  When those words come up in conversation, they are practiced with correct production.

Use His Interests:

Is there something that the child likes to do or work on?  If so, use that to practice speech sounds.