clinics and detoxes do the warm water dissolve method if they dont have the juice...and most 'done heads like the pills better than the methadose cherry liquid.. I dont think you can inject it with all the filler in those pills.
Honestly the best ROA would be to IV / boof them if you're into either of those. They burn so bad the pills are not worth snorting imo, that sting is all you'll be thinking about for 10-15 minutes. Smoking would be a complete waste but oral isn't bad to be honest.
Like 6 months ago, i got clean and then found 120mgs of methadone pills i stashed away. Ended up snorting like maybe 10mgs worth of powder just to scratch that "doing a line" itch and taking the rest by mouth and they hit me surprisingly hard. Took about 30-45 mins for them to kick in but when they finally did it knocked me out.