I tried the Coca Cola trick but with OxyContins and to be honest it was a waste, it actually felt weaker than if I just swallowed the whole ER pill. I don't know how it will work with morphine capsules because I never seen morphine capsules but I suppose it will be similar thing. Basically you put the pill ~50ml cola then leave it overnight in the fridge, by the morning the coat (capslue in your case) should become something like a gooey stuff and it will be big, like 3 times the normal pill size, that's why is important to make sure to put enough cola so it won't get dry while absorbing. Now some people say you have to remove the gooey stuff, other say you have to separe it from the core but still drink it because it contains part of the pill. I've tried both - it didn't work for me in both of the cases. But my results are with Oxycontins, not with capsules, they may have different structure, but if you read about the cola trick I suppose it's very similar. You can try it if you want it may have different effects on you, but also do not expect too much.
My advice is if you get the pills from a doctor ask him if he can give you the regular morphine pills, even if they are ER. I am currently taking M 100 light blue/grey pills which are 100mg morphine extended release and they are very easy to break/chew and work wonders for me. When you break/chew it, it works something between IR and extended release. The effect starts in 25-30 min but lasts for at least 7-8 hours instead of the IR which lasts only 3-4 hours. Just know that this is my tolerance, you don't have to take 100mg if you have low tolerance, you know yours better. Just to compare I was taking before 40mg Oxycodone IR and it didn't even make me high, it gave me slight buzz which lasted for 20 minutes and 1 hour after taking them it was like I didn't take anything. It was shit, because I had to wait 3-4 hours to take my next dose. I never took more than 40mg at a time even if my body was able to toletate it because I always prefer to be safe than sorry. It can take 1 wrong dose and everything can come to an end. So after I found the 100mg morphs I can say I live much better life. 1 pill keeps me for most of the day and it is a constant pleasant feeling, it doesn't get me high but for sure it is much better and pleasant that the oxys. For your case 20-30mg may be enough like I said it depends on your tolerance, but try to ask your doctor about the non capsule version of the pills. Sometimes different version of the same medicine can make huge difference. Sorry for the long post, I hope I helped at least little bit. And most importantly - stay safe!