I can't help _________ that the money could be put to better use.

Can't/Couldn't help (phrase): 
Meaning - If you can't/couldn't help something, such as acting in a particular way or making a particular remark, you are/were not able to control or stop it. 
- এ দুইটি phrase এর পর verb + ing হয়।
Example: He cannot help telling a lie.

Complete Sentence - I can't help feeling that the money could be put to better use.

তবে, Can't but এরপর verb এর base form বসে।
Example: She could not but congratulate him. 

Source: Cambridge Dictionary.